There is a lot of media currently about activities relating to the election of the current US President (Trump). While things like colluding with Russia may not be illegal some other activities may have been. (people are going to jail)
If Trump obtained the office of POTUS illegally, does that invalidate his presidency? What happens then?
Alternately, what if the person holding the office of POTUS was shown not to be legally entitled to hold the office? (not a US citizen, etc)
538 addresses the generic question What happens
So, is there a process for dealing with a finding that in essence invalidates an election?
There is a good bit of discussion but their answer is distilled:
When it comes to presidential elections, the answer is: not really. The laws and processes around national elections have grown up in a piecemeal fashion over time, with state and local laws governing the administration of presidential elections. And the Constitution itself focuses more on ensuring stability than on administering elections. As a result, there aren’t clear procedures for how to handle questions of legitimacy after the fact — especially when those questions involve the presidency.
Rather than reiterating that full discussion, refer to the article.
More generally, courts have overturned election results based on finding of fraud the the election process (as distinguished from voter fraud). I would refer to the Alabama Supreme court overturning a mayoralty election in Gunthersville, or the actual removal (from his office) of William Stinson in PA by court order on finding of election fraud.
There are two ways of interpreting "acted illegally". First is federal or state law. It is rather unclear whether the President can be held accountable under federal law in general. Even if it was established that the candidate did commit election fraud (at the General election or by corruptly influencing the electoral college), the FBI and the federal criminal court system do not have the authority to remove the president. As noted below, the Supreme Court could declare that a person is not President under the constitution. A state court could convict the President, but a state court would have no authority to overturn the federal election.
Then there is Constitutional law. There is little that actually binds the candidates in the constitution. Most of the requirements are on the union: "The exective power shall be vested in a President". Or on the various states: "Each state shall appoint...a number of electors...". The electors, the President of the Senate, the House of Representatives are all given specific requirements. If these are not followed then the President may not have been chosen constitutionally. But none of these are binding on the candidate.
There are various requirements on being a "natural born citizen". It is at least plausible that if it were discovered, after the fact, that the president was not eligible, then the Supreme court could rule that, in fact, no president had been chosen by the electoral college, and so the USA was contravening its own constitution. It could then direct Congress to select a President, as no eligible person had a majority of votes in the Electoral college.
The Supreme Court cannot remove a president, but it can declare that the person who claims to be president is not so.
It is possible for the President to have broken federal election law, in which case it may (or may not) be possible for him to face legal punishment. It is hard for a candidate to break constitutional law, as the constitution does not place many burdens on the candidates.
The only way to remove a sitting president through legal action is impeachment.
This requires the House to pass the charges against the president, i.e. articles of impeachment, and the Senate to hold the trial based on the articles and decide the outcome. Impeachment is a political process, not a legal one. Congress, if it has enough support, can toss a president out for pretty much any reason, as long as they can justify it to their electorate.
To gauge how such an effort might go, let's consider two recent events regarding this: the resignation of Richard Nixon, and the impeachment of Bill Clinton, and the fallout from both actions.
Nixon resigned rather than face the even greater disgrace of certain impeachment, essentially for lying about covering up the Watergate breakin. In truth, breaking into the Dem's campaign headquarters was a silly stunt that yielded nothing of real value, and did not affect the outcome of the election. McGovern's campaign was such a mess that he was going to lose no matter what. Relevant factors were Nixon's repeated public denials of having any knowledge of the breakin or the aftermath, shown to be false when the recordings of his conversations showed that he did authorize a coverup. Aiding the impeachment push was the disposal of the even less likeable Spiro Agnew... no one wanted him as president.
The Nixon resignation had a far reaching impact on the nation. The US went through a period of political turmoil in the mid to late 1970's, and looked very weak internationally. The fallout from that weak stature includes the Soviet invasion of Afghanistan and Iran taking the US embassy staff hostage. Not the only factor, but a very relevant one. Note that when a strong president was elected (Reagan), the Iranians coughed up the hostages very quickly, one minute after the inauguration.
And then there is Bill Clinton. In his second term, the House (under republican control) pass an article of impeachment based on Clinton lying under oath. Despite a crime having been committed (Clinton was disbarred from legal practice as a result), the Senate decided not to impeach.
Relevant factor in that was the perjury under question was more an embarrassing personal matter, rather than something that could have seriously affected the nation. The Clinton perjury was a fairly low key affair, not highly publicized, and certainly not repeated by him in numerous public statements. Also, most legislators remembered the fallout of the Nixon resignation, only 15 years in the past, and really didn't want to subject the country to that ordeal again. That would come back to haunt Newt Gingrich, speaker of the House who pushed the articles of impeachment through... he became politically insignificant after that.
It is possible that the new House could pass articles of impeachment against Trump. However, unless the articles outlined credible charges of serious malfeasance, the current Senate is unlikely to subject the nation to the chaos and weak international posture that followed the Nixon resignation. There just isn't sufficient reason, and the economy and employment situations are better than they've been for quite some time.
Even if the Dems recapture the Senate and have the capability to see an impeachment through, they would be well advised to proceed carefully. When the nation finally emerged from the shadow of the Nixon resignation with the election of Reagan in 1980, the Dems found themselves marginalized for quite some time after that. Economically, the late 1970's were not a good time for US citizens.
The electorate will hold the other party responsible for the outcome of an impeachment effort. And the outcome of a Trump impeachment will likely be declining economic conditions and problems internationally for quite some time... a Pyrrhic victory that could turn a lot of voters against the Democrats for at least a decade.
Yes, this is a very slippery slope to follow... if you consider what happens next.
(Some general comments that metastasized into a vague partial answer.)
Some answers speak of impeaching the president, but it's not obvious in what sense a faux official is the anything of anything. That is, suppose it's a generally known fact that somebody wasn't really elected; then there's no president to impeach, just an actor. And what of the actor's pretended actions? If an actor wrongly believed to be an official does not veto a bill which becomes law, is the bill still pending? Would the pseudo-reign of an actor be something like that of an antipope?
But suppose the remaining government is too confused or uncertain to know what to about it, and is further stymied by various opposing legal kludges and stopgap measures, so that paper and ceremonial certifications are believed sufficient to legitimize the actor.
Nevertheless a fake object isn't really certified, (it's an error in certification), and the sworn oath of a liar is meaningless. A court may compound the error, but that says less about what's genuine, and more about the indecision, timidity, or partiality of that particular court under difficult circumstances. Put another way, supposing in a corrupt era that every election was obtained illegally, then upheld by a court; elections would a ceremonial abusive ritual -- officials might call that "democracy", but it wouldn't be.
Government is not a toy. The unfortunate consequences of ignored truths can exert a stronger authority than any possible government. Corollary: a corrupt government that doesn't really govern diminishes its own sovereign power with every negligence, until at some point it is weaker than a formerly inferior rival force.
The outcome depends a lot on the actor's abilities and venality:
If the actor is a complete dud, inept, incompetent, tyrannical, and lacks sensible handlers, then things will get worse, and sovereignity will diminish.
If the actor is terrific and governs wisely, people may forget that it's acting, or consider it such good acting as to put up with it.
There are likely only two ways to remove a sitting President. The first is obvious - impeachment proceedings - but they're inherently political, so the question of illegality is less relevant. The second would be a successful Supreme Court challenge. There's absolutely no provision in the Constitution that would allow them to remove a sitting President, but they would get to decide exactly what their powers were. If the Supreme Court said that it had both the power and a reason to remove a sitting President I'm not sure, short of a quickly passed Amendment, what could stop them.
