(CNN)Republican presidential nominee Donald Trump suggested Wednesday night that he might not accept the results of the November 8 presidential election -- and that he would "look at it at the time."
Could Donald Trump legally challenge the presidential election?
Some of Trump's defenders compared his remarks to the aftermath of the 2000 presidential election, when challenges by Democratic nominee Al Gore to the results in Florida culminated in the Supreme Court's controversial decision in Bush v. Gore. Critics blasted Trump for subverting perhaps the most basic principle of our democratic system -- that election results, reflecting the will of the people, are sacred.
Here's our legal explainer of how Trump -- or Hillary Clinton -- can try to challenge the election if they appear to be on the losing side at the end of election night:
Yes, but not at the national level. US elections, even for president, are administered on a state-by-state basis. Every state has its own laws governing elections, including laws that allow (and, in some circumstances, require) that the vote be recounted if the preliminary results show a very close outcome in that state, regardless of what happens elsewhere. State laws also identify other exceptionally narrow circumstances in which challenges can be brought. And in any event, every state also has procedures for counting absentee and provisional ballots, many of which are counted after Election Day.
What this means in practice is that the results that are reported on election night are, both practically and legally, preliminary -- and may very well be subject to change in the days and weeks to come depending upon the different ways each state finalizes its results and resolves close calls.
We all remember Florida in 2000 because the margin between Gore and George W. Bush was razor-thin and because whoever won Florida would cross the 270-vote threshold in the Electoral College -- and thereby win the election. Fewer folks remember New Mexico that year -- in which the vote was even closer than it was in Florida, and in which it took 23 days to certify the final results -- because the outcome wouldn't have tipped the scales nationally either way (Gore won the state's five electoral votes).
This is why, when presidential elections are not as close (for example, in 2008 and 2012), there's far less talk of challenges or recounts. Some states may still be decided by razor-thin margins, but not enough to make a difference in which candidate received 270 or more electoral votes.
Thus, the larger the apparent margin in the Electoral College on election night, the harder it would be for the losing candidate to legally challenge the election -- since he or she would have to succeed in overturning the results in enough states to change the outcome in the Electoral College.
Every state's election laws are different. At the risk of oversimplifying, there are usually two different sets of issues: Whether state law requires the state to conduct a recount and whether state law allows one of the candidates to request a recount or some other kind of relief (e.g., whether absentee ballots without postmarks should or should not be counted).
Either way, most states' laws impose a statewide deadline for certification of the final state-wide results, and a federal statute -- the Electoral Count Act of 1887 -- imposes a pair of deadlines that tend to drive the timing: a "safe harbor" deadline that guarantees that a state's chosen slate of electors will be recognized by Congress only if the state's results are certified within 35 days of the election and a requirement that the electors -- the state's representatives to the Electoral College -- be appointed 41 days after the election.
In a nutshell, then, states usually have five weeks to resolve any challenges to the preliminary results. They can take longer, but they then run the risk that Congress would not recognize the state's reported results (and would instead decide for itself who won the state).
Unless the challenging party can show some kind of federal constitutional violation (which is exceptionally rare), almost every challenge to preliminary election results is resolved under the relevant state's law. And in every state, the authoritative meaning of state law is up to the state supreme court, which will usually have the last word in any dispute over the mechanics -- or result -- of any post-election challenges.
Of course, the final arbiter of presidential elections under the Constitution is the US Congress, which, by law, meets to count the electoral votes in a joint session on January 6.
One of the purposes of the Electoral Count Act of 1887 is to make this joint session a formality, but if there are lingering disputes arising out of states that did not meet the safe harbor deadline, it is up to Congress to settle them. And if, upon counting the electoral votes, Congress determines that no candidate has received a majority (which has happened three times -- in 1801, 1825, and 1877), the Constitution provides that the matter will be resolved by the House of Representatives, with each state casting one vote.
In almost every case, no. As noted above, most of the legal questions that could arise in states with contested results are state law issues that are beyond the Supreme Court's jurisdiction.
What made Florida different in 2000 was the Supreme Court's determination that the unique manner in which the Florida state courts had ordered a manual recount violated the US Constitution -- to wit, the Equal Protection Clause. Because the Supreme Court thereby prevented the recount from going forward, and because the "safe harbor" deadline was the same day as the justices' ruling, the decision had the practical effect of ending Gore's ongoing challenge to the results.
But because of both the uniqueness of the constitutional violation in 2000 and the controversy surrounding the Supreme Court's role in the election, it seems highly unlikely (all the more so with the court operating with only eight Justices) that what happened in that year could repeat next month.
It depends on the "results" to which the candidate is referring. If he or she means the preliminary results announced on election night, they are under no obligation to "accept" those results if the margin in a large enough number of states is close enough that recounts might somehow change the national outcome. Indeed, as noted above, some state's laws might automatically require a recount if the results are sufficiently close.
But if he or she means that they might not accept the final results as certified by each of the states, as voted upon by the Electoral College, and as confirmed by Congress, that would be unprecedented in American history.
Steve Vladeck is a CNN contributor and professor of law at the University of Texas School of Law.