Looking at American politics, it seems like there is a tremendous animosity between people with different political leanings. Was it always this polarized? If not, when did this trend begin and why?
*Edit: As per a comment by @jamesk, I am editing this question. These hard feelings are true all across the world. Was the world always so polarized? When or how did this begin?
Polarisation is not entirely new, but it’s not a constant either. Looking just at US national politics, there have been other periods of very strong polarisation (e.g. the late 19th century, following the Civil War), and other periods of comparative consensus (e.g. the mid–late 20th century, during the Cold War).
Fivethirtyeight.com has run quite a few articles on this topic, looking at various quantitative measures of polarisation through recent US history. A good recent run-down is Geoffrey Skelly’s Why a Biden blowout didn’t happen…, and more can be found under their polarization tag. Broadly, their analyses support the claim that on a historical scale, the current polarisation is not unique or extreme; but it is the most polarised that US politics has been since WWII, so within living memory for most Americans, it is new.
(Other answers give further good points which I won’t repeat, especially comparisons in a broader international and historical context.)
Personal animosity between political opponents is widespread and historic. It is particularly common in democracies.
In an oligarchical or dictatorial state, power and influence depends on your closeness to the dictator, and the dictator tends to surround himself or herself by people of the same opinion. In a democracy, people of differing views are brought together to debate, argue and in some cases this leads to personal animosity and even fights.
Examples abound, from Ancient Athens, where votes to expel (or ostracise) people reveal Athenians’ attitudes toward their fellow citizenry. Some feature nasty epithets: “Leagros Glaukonos, slanderer;” “Callixenus the traitor;” “Xanthippus, Ariphron's son, is declared to be the out-and-out winner among accursed sinners.”
Civil war politics included several fights in Congress included one in which an abolitionist Senator was nearly beaten to death for insulting and publicly mocking a pro-slavery Congressman.
There are, of course, plenty of counterexamples. Fierce political enemies who are good friends (Frank Fields and Nicholas Soames) or even marriages (John and Sally Bercow).
In America in the period 1940-1980 there was a period when the clashes were within, not between the parties. And there was the real enemy of Nazis or Communist Russia that both parties could unite against. This period may make us think that bipartisan politics is the norm. America is also unusual in that the President often requires support from at least some members of the other party to appoint his/her cabinet and get legislation passed.
The breakdown of this bipartisan politics began under Ronald Reagan (who followed an economic policy that, unlike his predecessors, didn't attempt to be centerist) and accelerated under Obama and particularly Trump. Trump's personal style is to insult and belittle his opponents. This get his supporters and opponents emotionally involved. And where emotions rule, there is little room to "see the other side" or "respectfully agree to differ".
Newt Gingrich as Speaker of the House was the watershed moment.
Soon after his House Speakership he managed to get the government shut down for a fairly long while.
His "throw the bums out" presaged the Tea Party (and Trump's rather amusing claim to "drain the swamp"). Sure, Pat Buchanan also had that kind of message (peasants are coming with pitchforks), but he was more of a wild man than a major insider.
It wasn't enough to campaign on policies, Newt really set out to paint the opposition as unacceptable as the opposition. And anyone within his party who was willing the compromise (you know, to actually get things done in government) as a traitor.
Quoting Wikipedia:
A number of scholars have credited Gingrich with playing a key role in undermining democratic norms in the United States, and hastening political polarization and partisan prejudice.[7][8][9][58][59][60][61][62][10][63][64][11] According to Harvard University political scientists Daniel Ziblatt and Steven Levitsky, Gingrich's speakership had a profound and lasting impact on American politics and health of American democracy. They argue that Gingrich instilled a "combative" approach in the Republican Party, where hateful language and hyper-partisanship became commonplace, and where democratic norms were abandoned. Gingrich frequently questioned the patriotism of Democrats, called them corrupt, compared them to fascists, and accused them of wanting to destroy the United States. Gingrich furthermore oversaw several major government shutdowns.[65][66][67][59]
University of Maryland political scientist Lilliana Mason uses Gingrich's instructions to Republicans to use words such as “betray, bizarre, decay, destroy, devour, greed, lie, pathetic, radical, selfish, shame, sick, steal, and traitors” about Democrats as an example of a breach in social norms and exacerbation of partisan prejudice.[7] Gingrich is a key figure in the 2017 book The Polarizers by Colgate University political scientist Sam Rosenfeld about the American political system's shift to polarization and gridlock.[8] Rosenfeld describes Gingrich as follows, "For Gingrich, responsible party principles were paramount... From the outset, he viewed the congressional minority party's role in terms akin to those found in parliamentary systems, prioritizing drawing stark programmatic contrasts over engaging the majority party as junior participants in governance."[8]
In the larger picture, not just the US, the world has become more polarized even as mainstream Western parties have largely converged to a center-left/center-right set of economic policies:
Large scale Socialist nationalizations a la Mitterand have been shown not to work. Thatcherism stopped England's gradual descent into economic irrelevance and British voters were not keen on bringing back the good old days via Corbyn. Yet, a hard Thatcher-style position, with mass privatizations and anti-union stance would surely lose modern elections.
Reagan-style trickle down ended up not trickling down very much but Clinton was able to run a surplus and was generally popular running a somewhat center(right) set of policies, something also done by Tony Blair.
Any Ayn Rand style wild dreams of Libertarian economics have remained just dreams and don't attract many voters. Balancing budgets has ceased to be a priority for most right wing parties.
Outside the US, policies such as public health care are now the norm across the board.
Even places like Sweden have gradually retrenched their tax burden and relaxed taxes on the rich. At the same time, Western economies slice of government GDP has ballooned up as the government is expected to provide many services.
Meanwhile, the West is under massive stress. Accustomed to centuries of dominance over the rest of the world we now are competing with them. Between globalization, automation and ever greater need for education in many jobs, many blue collar jobs that would have provided adequate living in decades past have gone. Even white collar jobs are facing outsourcing and automation. No mainstream party has found an answer (nor is it clear what it would be if it even exists).
In short, even as the substance of economic policies converged, the parties seem to have become ever more strident in denouncing each other. Dissatisfied voters, whipped up by social media and unhappy with the status quo kept by the main wings of their respective parties, have increasingly supported positions on the fringes. You can see this in France (Melanchon and LePen) or Italy (Lega and 5 Stars).
So while I agree with other answers that we have been more polarized in the past, those were also times when the main parties actually had massively divergent positions on how to run a country, unlike now.
Quite frankly, politics has not always been this polarised. It has often been worse. A couple of examples:
At the time about half of the states of the US rebelled against the Union and seceded to form their own country. The reason for this was the abolitionist platform of the Republican Party at the time which threatened the economic backbone of large areas of the South: slavery-based agriculture. It bears noting that the President, whose election triggered the aforementioned events, had frequently stated he had no intention to abolish slavery and believed it outside of his rights to do so.
The interwar period is taught as a particularly violent period of German history. Among high-profile names, Karl Liebknecht and Rosa Luxemburg, former socialdemocratic politicians that later split off to ultimately for the Communist Party, were assassinated by Freikorps, right-wing paramilitary units often recruited from war veterans.
Aside from these two, there were clashes between communist supporters and right-wingers all through the 1920’s and the Nazi party famously had its own paramilitary, the SA.
In Russia, the Russian Revolution(s) of 1917 led to a struggle between more conservative political forces and socialist ones which evolved into a civil war between the Bolsheviki and the centrist White Army. A very similar development occured in Finland where most of the city of Tampere was destroyed in the civil war of 1918.
In general, political assassinations form a bloody line all through history.
In the examples above I have concentrated on western countries at a time when political parties similar to present day ones existed. It should be noted that political violence is not constrained to these geographic areas nor these timescales as the James’ answer shows. Also, I have just picked out four significant raisins ignoring a multitude of other possible examples to keep the answer short.
It's difficult to answer this objectively over long periods of time owing to lack of comparative instruments. If we restrict discussion to the US Congress voting record, it's probably the longest-track instrument that can be used. To get just one graph (on US House of Representatives) which goes back to the 45th Congress (1879) from a related question
Measurements at larger population level are stymied by lack of polls that consistently asked the same question, so only a narrower time frame can be compared, e.g.
Using data from the American National Election Study (ANES), the figure shows trends in average feeling for the party participants identify with (in-party) and for the opposing party (out-party). In-party feeling (green line) has remained high over the period plotted, though it has decreased slightly in recent years. Out-party feeling (purple line) has decreased dramatically, especially after 1990.We also plot affective polarization (gray line)—the difference between mean in-party feeling and mean out-party feeling—which shows a significant increase over time (Iyengar et al. 2012), mainly due to an increase in animus against the out-party. However, it is worth noting that affective polarization actually decreased between 2012 and 2016 due to decreases in feeling toward the in-party.
As you can see polarization has been increasing in the US in the past 3 decades by most measures, but at least based on Congress data, it was just as high in the 1930.
Measuring polarization for more than two parties (which relevant for many other non-US countries) is somewhat more difficult, methodologically, as there are multiple valid measures of polarization even for the same data. Again owing to data about parties being more easy to get than for the public in other countries too, the X axis in the following graph is relevant. As you can see polarization went up in some countries more than in others.
Again, whole population measures aren't usually available except for shorter time frames:
The US trend since the 1980 isn't reflected in (many) European countries up to 2010 or so. But note that this data (owing to time frame in that study) does not cover the more recent rise in the populist right in Europe.
And of course, if by "world politics" you mean relations between countries, that's more difficult to quantify, but surely the Cold War and World Wars before that were periods of higher polarization in that sense. (Someone even predicted the "end of history" as the Cold War was ending...)
The book "Why We're Polarized" by Ezra Klein takes an in-depth look at the polarization of the United States specifically. One main source of polarization identified in this book was the realignment of political parties in the 1960's around the passing of the Civil Rights Act. Up until that time, the Democratic party was composed of two main factions: Southern Dixiecrats (who were notably opposed to civil rights legislation that would improve the lot of Southern African Americans) and Northern Democrats (who cared about passing progressive legislation such as the New Deal but relied on Dixiecrats to win). This uneasy alliance:
"kept the Democratic party less liberal than it otherwise would've been, and the Republican Party congressionally weaker than it otherwise would've been, and stopped the two parties from sorting themselves around the deepest political cleavage of the age". - pg. 31
Northern Democrats broke with Southern Dixicrats and allied with some Senate Republicans to pass the Civil Rights Act (though Republican presidential nominee Barry Goldwater notably opposed the Civil Rights Act, thus cementing the identity of Democrats as the party that passed bill and Republicans as the party that opposed it.) In the fallout, Dixiecrats largely realigned themselves with Republicans following it's anti-civil rights leader Goldwater. From there, it was much easier for the parties to drift apart because ideologically, they now fell on opposite sides of the spectrum regarding race, civil rights and progressivism to a larger extent.
So far, no answers have mentioned Duverger's Law.
This states that the pressures under the plurality (first-past-the-post) voting method push toward 2-party rule. With centrists and third parties pushed to the sidelines, voters are forced to "pick a side", increasing polarization.
With the information age permitting massive, nationwide coordination throughout each of the major parties, this process has only gotten more efficient with time.
For most of the 20th century, the US had a strong contingent of what, for lack of a better term, I will call "reasonable people" -- not precisely centrists, but people with no great investment in any ideology, neither activists nor wishing particular harm on anyone -- and willing to stay out of their neighbors' lives as long as the neighbors stayed out of theirs.
This group moderated the two party system because if they perceived one party taking too hard of a stance, they would be entirely willing to vote for a candidate of the other party. The parties had to take some stands to distinguish themselves and attract voters, but not so many as to alienate the bulk of voters.
With the coming of cable news and the internet, this group has seemed to evaporate. The result was a feedback effect: the parties felt comfortable taking stronger stances, moving their positions further apart, which made it less likely for voters to ever consider changing sides, which led he parties to radicalize their positions yet further. News coverage of presidential elections used to talk about candidates courting the swing voters, but by 2004, "has anyone ever seen a swing voter?" was the joke of the day.
There used to be liberal Republicans and conservative Democrats. This Doonesbury comic from 1994 was from the tail end of that era. Data pretty consistently bears this out.
Forces have been pushing increased polarization on this issue for a few decades now. I do not personally know a time when "liberal Republican" was not an oxymoron, because by the time I was old enough to pay attention to the news and follow politics, this shift was already close to over.
Essentially, there is a serious and fundamental disagreement over what kind of government we should have. There are two main sides, each one having more or less taken over one of the political parties. It goes back to the New Deal, which dramatically expanded the reach of the federal government and the kinds of things it spent money on, and how much money it raised in the form of taxes. It was controversial then, and it's basically never stopped being controversial since.
As a rule of thumb, it goes along with the (micro)economy. When people has jobs, and those jobs pay a decent liveable wage, people is happy going on with their lives and doesn't care too much for politics. Whenever life gets tough on common people, they start looking at politicians for solutions, and when they don't come, they get angry.
There was a lot of political trouble in the beginning of the XXth century, then it became even worse in the years of the Great Depression, with the societies of the whole world bitterly divided among fascists and communist with almost no middle ground between; then everything went incredibly smoothly in the 50's and 60's despite the Cold War and the possibility of nuclear extinction, thanks to the wonder years of post-WWII economic expansion and, lo and behold, now that having multiple jobs isn't enough to make ends meet, polarization is on the rise again.
Many studies have been made on politics polarization. Unsurprisingly, many noted the strong correlation between unequality and economy stagnation and polarization. This study signals that unequality and trust are the highest predictors of polarization, followed by real GDP. Another one studies the correlation between economic and racial conflicts and its effects over polarization, concluding that identity politics and unequality positevely feedback each other and both increase politics polarization - they note, interestingly, that while unequality does increase polarization, reducing unequality after it has risen to a certain level does not inmediately decrease polarization. In any case, polarization is certainly cyclical and strongly tied to the economy of the commons - it does not matter if the economy of the country is supposedly doing ok, it's the layman's pocket what matters.
