President-elect Donald Trump addresses supporters at an election night event on Tuesday in New York. (Jabin Botsford/The Washington Post)

The extraordinary happened: Donald Trump will be the 45th president of the United States. To those who voted for Trump, congratulations. I hope Trump will be the positive version of the leader that you hoped he would be when you voted for him. To those who can’t quite believe this is happening — that someone so far from the mainstream of American political thought could win a presidential election — I want to focus on a question likely to be very important in the future: When Congress considers exercising checks and balances on the power of President Trump, what is the break point? At what point does Congress decide that Trump has gone too far and should be countered?

Here’s why I think this is really important. The modern presidency comes with extraordinary power. The president has power over the entire executive branch, from the military to the Justice Department to the FBI to the administrative state. The Constitution provides for a number of checks on that power. The courts provide some very important checks, of course, at least when cases get to them.

But the most important checks on a president come from Congress. On a routine basis, the president needs Congress to enact laws that allow and pay for what the president wants to do. The president needs the Senate to confirm nominees. And at the very extreme end, the president needs to avoid an outright rebellion in Congress that could lead to impeachment and removal. As a result, how far Trump can go depends a lot on how far Congress will let him go.

But here’s the interesting thing: Whether Congress counters presidential power depends on judgments about whether the president has gone too far. Those judgments aren’t set in stone. They’re mushy sorts of judgments based on what seems “on the wall” vs. “off the wall.” Presumably there is always a break point somewhere — a point at which Congress changes direction and counters a president who has seemingly gone too far. But where that break point might be is a political and cultural question that depends on a mix of public opinion and the views of those serving in Congress.

I mention this because Trump was remarkable as a candidate for how little he followed traditional conventions. Throughout the campaign, Trump would do seemingly outrageous things that many thought would sink his candidacy. Trump enthusiastically embraced what was “off the wall.” You know the list by now. He celebrated mob violence. He advocated war crimes. He urged the criminal prosecution of his opponent. He invoked conspiracy theories. You would have thought, before 2016, that a candidate couldn’t do that without losing tons of support. The American people just wouldn’t stand for it. And yet voters this time apparently didn’t mind. What we thought was going way too far was apparently not considered too far at all. The old standards no longer apply.

Now maybe the Trump we saw as a candidate was not the Trump we’ll see as president. Trump has changed his mind before. Maybe the vindictive authoritarian streak seen in Trump the candidate won’t be replicated in office. I certainly hope that’s the case.

But let’s assume that the nasty side to Candidate Trump is carried over to the White House. If so, where is Congress’s break point? Where is the point where members of the House and Senate will say, in response to what Trump has done, that he has just gone too far? Congress is a “they,” of course, not an “it.” Different members will approach these issues differently. But the checks and balances of Congress really depend on these collective judgments.

For example, will Congress follow the old standards, opposing the new president when they would have opposed presidents like Clinton, Bush or Obama? Will the old rules of propriety still apply? Or will Congress react to Trump’s victory by moving the break point, letting Trump be Trump because apparently that is what the voters want? And if Congress moves to a new break point just for Trump, how far will that point move over time?

For Democrats, this is a relatively easy set of questions to answer. They’ll be the opposition. I gather they’ll oppose Trump in the usual way. The harder and more important question is how Republicans will react, especially in the Senate. The House and Senate will stay in Republican hands in 2017. For Republicans in Congress, Trump’s base is largely their base. Opposing Trump will mean going up against their base, at least so long as Trump remains popular within the GOP. For these politicians, where will the break point be?

Here’s an example to make my concerns concrete. FBI Director James Comey is serving a 10-year term that is set to expire in 2023. Comey has been a lightning rod of controversy this year. Justly so. But whatever you think of Comey’s judgment, he is very independent. Comey is the guy who famously stood up to President George W. Bush over illegal surveillance, ready to offer his resignation from the Justice Department, in 2004. If you’re looking for a check on lawlessness from President Trump, Comey is actually a good place to start. It may seem counterintuitive now, when a lot of people fear that Comey helped Trump win the election. But I think it’s a good bet going forward.

Say President Trump wants the FBI to do something that Comey refuses to do because it’s likely illegal. The traditional view would be that it’s tough for the president to fire an FBI director for that reason (or to have the FBI director resign for that reason) because the political blowback would be severe. Sure, the president has the legal authority to do it. Just ask William Sessions. But firing the FBI director for refusing to break the law would traditionally be thought to hit a break point. It would raise a lot of fears about the FBI’s independence, and it would trigger a strong political response from Congress. In all likelihood, it wouldn’t happen.

But will the next Congress apply those old norms to President Trump? Imagine Comey refuses an illegal Trump order. Trump promptly fires Comey, and he then nominates a Trump loyalist to be the new FBI director. How would the Republican Congress respond? Would senators say, “well, Trump is Trump,” shrug it off and confirm Trump’s pick? Or would they rebel against Trump not only for the illegal order but also for removing an independent FBI director who merely wanted to follow the law? And is their judgment going to be their own view, or are they going to defer to what the polls say or just what the GOP base and talk radio thinks?

That’s just one example, of course. You can ask the same questions about the full parade of horribles that Trump critics fear from a Trump presidency. Maybe we’ll get lucky and Trump won’t go there, making these concerns moot. But if he does, figuring out the break point will become the question on which the country’s future rests. The fear among Trump critics, of course, is that a Trump presidency would see the same-party break point move so far that the checks and balances the Constitution provides will be more symbol than force. Time will tell. As always, stay tuned.