I have over the years seen political pundits talk about whether a president-elect will accomplish such-and-such thing within his first 100 days in office. What's so special about that span of time? Why not say "first 3 months", or "before summer", or "in the first year of his term"?

Is it just arbitrary and 100 is a nice round number, or does anything politically significant happen around that time?

  • 8
    Nothing politically significant happens. It's just a way for the 24 hour news networks to cash in on the presidential election ratings extravaganza one last time.
    – J Doe
    Nov 16, 2016 at 22:18
  • To whoever gave this comment 5 upvotes - there actually are politically significant changes after 100 days. I cited evidence in my answer. This comment is funny and pithy and 100% wrong.
    – user4012
    Nov 17, 2016 at 2:34
  • @user4012 -- Agreed; the phrase wasn't meant to be interpreted literally. Relatively speaking, its much better than when politicians say "in my first day in office"; now that is indeed ridiculous because very little can be done that quickly.
    – Fine Man
    Nov 18, 2016 at 2:15

3 Answers 3


There are several reasons:

1. "honeymoon period" with Congress in first 100 days

This is a period when there is less resistance to him. This is more pronounced when President and Congress are not united.

This was covered by research by Casey Dominguez, Department of Political Science at UCB. There are two different papers he published on the topic:

  • "The President’s Honeymoon with Congress: Explaining Reagan’s 1981 Victories" (2002)

    ... empirical evidence that presidents have honeymoons in their relationships with Congress during their first hundred days in office.
    Presidential support scores and other quantitative indicators of the legislative records of seven newly inaugurated presidents indicate that presidents who face divided government should expect to be more favorably treated during their first hundred days than they will be later in their administrations. The same honeymoon effect is not as evident for presidents who face unified government.

  • "The Honeymoon Effect: Investigating Individual Members" coauthored with Buchler (cache).

    Conventional wisdom has long held that newly elected presidents have a so-called “honeymoon” with the Congress. Recent research has modified this conventional wisdom by showing that only presidents who face divided government have higher win rates during the first hundred days of their first year in office than during other periods. Existing work, though, does not identify the mechanism that produces this effect. In this preliminary paper, we search for the origins of the honeymoon effect by comparing Members’ of Congress presidential support scores in a president’s first and second years in office. We find that measuring the honeymoon effect at the level of individual Members of Congress gives a very different picture of who had a honeymoon, and that the honeymoon seems to be driven by increased presidential support from marginally party-loyal Members of both parties during the first year in office.

2. A "honeymoon period" with the Press coverage.

Quoting from Dimonguez's paper above, in prior research (this is mentioned in both papers)

In their study of the press’ treatment of the president, Michael Baruch Grossman and Martha Joynt Kumar (1981, 259-265; 275-279) found that during the inaugural year, the press covered the president in greater volume and in a more positive light than later in the term. Their analysis showed that early coverage was favorable to presidents because reporters rely heavily on official White House briefings while they develop their own administration sources, and because reporters and editors believe announcements of policy proposals and profiles of new Members of the administration are inherently newsworthy. If conflicts or scandals emerge in the first few months of a presidency, the press will cover them in ways that might be perceived as negative toward the president, but barring major mis-steps, presidents can expect their press coverage to be neutral or positive.

(Unless you are Trump. All bets are off there, it's a hate-hate relationship, he even ticked off Fox News, for better variety :).

3. Also a "honeymoon period" with the public, partly caused by favorable press coverage.

Reasonable people will give you SOME benefit of the doubt before judging you on what you did.

Partially in response to that favorable press coverage, the president has been found to have a honeymoon with the public during his first few months in office. Approval ratings are stable and higher than average during their first few months. ... At the beginning of an administration, when polls ask whether respondents approve of the job the president is doing, partisans of the president respond by saying they approve of his performance, as do a sizeable number of independents and opponents who will change their minds once he actually builds a record on which to make judgments. Many others offer “no opinion”(Brody 1991, 28-44).

4. Better success with actual bills.

Research also shows that presidents have higher “success rates” when they take positions on bills before the Congress during their inaugural year than they do later in their terms (Dominguez 2005; Lockerbie, Borrelli and Hedger 1998).

Why 100 days specifically?

It's a nice very round number, perfect for a soundbite and a meme.

I wasn't able to find any conclusive proof, but following Wikipedia links, there appear to be two "scholarly" speculations:

  • Overall term and 100 days idea is claimed to have been originated with Elba-to-Waterloo period of Napoleon Bonaparte's return (source: Alter, "The Defining Moment: FDR's Hundred Days And the Triumph of Hope")

  • In politics, the claim is that FDR originated the term, by referring to (accidentally being exactly 100 day long) period of 73rd Congress session that created the New Deal. Ironically, that was NOT FDR's first 100 days as President.

So, why ~3-3.5 months?

Several likely reasons, all my speculation:

  1. Less than 3 months, and you can't really get anything much done worth making into a memorable list.

    • Partly, because you need to assemble the team of higher ups AND hire underlings.

    • Partly, because a lot of things just need time to achieve, even the quick ones.

    • Partly, even for quick achievables, you only have so much bandwidth as administration, so you won't have a large and nice list to point to for a first week or two.

  2. More than 3 months, and the honeymoon periods discussed above are over

  3. More than 3 months, and attention span wavers.

  • I suspect #4 relates to #1, the way that #3 relates to #2. I'd also explain both #1 and #4 as relating to a (hypothetical or real) "mandate" that the President can claim to have after an election. I think your speculative reasons at the bottom are likely accurate, though. It's a round number, and just enough time to try and get things done.
    – Bobson
    Nov 17, 2016 at 1:37
  • @Bobson - yes, probably they are related that way. But I didn't see any research to back that up, so didn't voice that idea.
    – user4012
    Nov 17, 2016 at 1:43
  • I suspect #3 has a lot to do with the fact that most–well, a lot–of the people had just voted for him because they expect him to do a good job. And like you mentioned for #2, Trump is an exception. Nov 17, 2016 at 2:53

According to a Wikipedia stub article, the term may have originated with FDR, and the things he accomplished rapidly at the beginning of his administration (or the accompanying Congressional session). According to Obama's "100 days" page, it's been a fairly standard benchmark of a President ever since. This article compares some of the other Presidents in between those two.

It's also a concept that's fairly well entrenched in the business world. As some examples from there:

That last link even says "Starting off on the right foot is crucial, especially during 'the first 100 days,' when new top executives are under intense scrutiny to prove they’re equal to the job".

  • Hope you don't mind I stole your Wikipedia link (or rather, its sources)
    – user4012
    Nov 17, 2016 at 1:28
  • 3
    Thief! Thief! Someone call the StackCops! @user4012 just ran off thataway with my links! :p
    – Bobson
    Nov 17, 2016 at 1:33

I do not know if that translates well into USA politics, but traditionally in Europe the 100 days is a "courtesy time"1 while the opposition2 tries not to be too obstructionist against a newly elected government, to let it show its "true colors" (if it is willing to compromise and negotiate their measures, if it will try to rule without counting with other parties, how radical are its proposals, how open it is about its projects and activities).

This is more important in Europe where governments are often formed by an alliance between different parties, which usually leads to some initial frictions.

In any case, in the face of the government taking measures too aggressives (proposed laws, controversial appointements of government members, etc.), it is not unheard of opposition parties declaring that this period has ended before the 100 days are over.

The "100" number is just a convenient, round number.

1And as such, not mandatory but usually enacted.

2And yet more informally, the media.

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