Within the next few weeks, every member of the House and Senate will make a public declaration of their judgment of President Trump’s misdeeds. While each has their own beliefs and their own incentives, the politics of impeachment are much simpler and more straightforward than you might think.

There are no double bank shots to be played, no mass public conversions that can be engineered and no clever stratagem that will transform the outcome of this process. Which ought to be liberating, at least for most members of Congress.

Let’s start with the state of overall opinion. Before the impeachment inquiry began, Democrats hoped it would turn the public more against Trump than they already were, and Republicans hoped there would be a furious backlash from their own voters. What we saw instead was something simple. As FiveThirtyEight’s tracking shows, before the Ukraine scandal broke, around 38-40 percent of Americans thought Trump should be impeached, and around 50-53 percent thought he shouldn’t.

But since the scandal broke, around 48 percent think he should be impeached and around 43-45 percent say he shouldn’t. Any given poll may produce a slightly different result, but that’s the general pattern.

If you’re a member of Congress, the national picture doesn’t matter nearly as much as what your own constituents think. But whether you’re in a swing district or one that votes overwhelmingly for your party, your calculation is essentially the same: If you go against what your party believes, you’re basically doomed in the next election.

Which you can see in the strange case of Rep. Jeff Van Drew (D-N.J.), the exception that proves the rule. Van Drew opposes impeachment, which is apparently a belief he holds sincerely and strongly enough to sacrifice his political career over it. Though Van Drew was elected last year to represent a district Trump won narrowly in 2016, the New York Times reported that he recently saw a poll showing that “the overwhelming majority of Democratic primary voters — 71 percent — would be less likely to support his re-election if he opposed the charges against Mr. Trump.”

Voting against impeachment would have gotten Van Drew a primary challenge that he’d likely lose. So he took another path: He’ll be switching parties, and come next year, he’ll be challenged in the primary by a genuine Republican and probably lose.

Contrast that with Rep. Elissa Slotkin (D-Mich.), who also represents a district Trump won in 2016. Rather than try to save herself with some complicated switcheroo in a vain attempt to win over Republicans in her district, Slotkin decided to vote yes on the two articles of impeachment and is now explaining to her constituents why she made that decision.

Slotkin is smart enough to realize that doing so will preserve her support among Democrats in her district while probably not alienating any Republicans who weren’t already going to vote against her. Other vulnerable Democrats seem to see it the same way, which is why one after another is saying they’ll vote in favor of impeachment.

These Democrats likely understand that swing districts aren’t made up of moderate voters, they’re made up of roughly equal numbers of partisan Republicans and partisan Democrats. Whichever party you’re in, voting for the other side won’t get you much credit with them, but it will destroy your support among your own partisans.

Which means that the best thing for Democrats in swing districts (and states) isn’t finding some kind of middle way. It’s making sure that Trump is as discredited and damaged as possible.

And that’s fine with Democrats, since there are probably very few if any who secretly think Trump is innocent but are feeling pressured into supporting impeachment (though I’ll predict that Sen. Joe Manchin III (D-W.Va.) will vote against removal).

On the other hand, there may well be any number of Republicans who feel the opposite. Former senator Jeff Flake claims that “at least 35” Republicans in the Senate would vote to remove Trump if it were a secret ballot. The number might not be that high, but some certainly understand how obvious Trump’s guilt is.

But they face the same simple calculation, leaving no incentive to vote against him.

We can’t be sure about how this will affect next year’s presidential election, since no president has run after being impeached. But in all likelihood it will follow the simple pattern we’re seeing so far. Democratic and Republican voters are both energized by it, which will contribute to an election likely to have extremely high turnout. A small but meaningful number of unaffiliated voters might be pushed away from Trump by what has already been revealed and what might still emerge. And even if they aren’t directly persuaded to shift their opinions on the president, it will reinforce the other arguments Democrats make about Trump being corrupt and dangerous.

So where does that leave us? Impeachment was always the right thing to do substantively, because Trump’s misconduct was so clear and egregious. And it’s the right thing to do politically, because it builds up the case about Trump’s fundamental corruption even if it doesn’t result in his removal. Everything else is details.

Read more: