Polls close shortly in four states that were key, in different ways, to President Trump’s success in the 2016 election. Indiana, where his vice-presidential pick helped solidify an already-red state. North Carolina, where the race wasn’t as close as expected. Ohio, no longer a swing state, where most of the areas bordering Appalachia voted overwhelmingly for his candidacy. And West Virginia, which went from deep blue to dark red in less time than it would take a baby to be eligible to vote.

The swings in Ohio, Indiana and West Virginia, in particular, embody the story of Trump’s victory. They are places with large populations of voters targeted by his sales pitch to white working-class voters frustrated at America’s cultural and social evolution.

That said, though, these are not places that Trump and his party can entirely take for granted in November. Between the four states, there are 41 House seats, all but eight of which are held by the Republicans. Of the 33 others, though, almost a third are rated as vulnerable by Cook Political Report.

One of those districts is in Indiana, the 2nd Congressional District. On the graph below, the vote in each congressional district for the past three presidential elections is shown using data from Daily Kos. Instead of showing the actual vote in each district, though, we show the vote relative to the national margin. So if a district backed Trump by five points in 2016, it was about eight points more Republican than the country on the whole (since Hillary Clinton won nationally by about three).

That shows us that nearly every district in Indiana has shifted fairly steadily to the right since 2008. That includes the 2nd District, which Cook rates as “likely Republican,” the safest of its vulnerable-seat ratings. Only one district, the 5th, went back to the Democrats after 2012.

The question for which we don’t yet have an answer is what happens in districts in which Republican incumbents face difficult challenges in November. Before the primary, there is value in embracing Trump given his popularity with Republican voters. After, that’s less the case, given that most Democrats and independents disapprove of the job he is doing.

In Indiana, there aren’t many districts where that’s the case. In North Carolina, there are more.

Three House districts in North Carolina are rated as vulnerable by Cook, including the 9th and 13th, each of which is rated “lean Republican.” In North Carolina, several House districts actually shifted toward voting more Democratic than the nation in 2016, including the 2nd (rated “likely Republican”) and the 9th. All three seats held by Democrats did, too.

Out of Ohio’s 16 seats, five are considered in play by Cook. The 12th is considered a toss-up after the resignation of Rep. Patrick J. Tiberi (R) this year. (There’s a special election in August to fill the vacancy until January.) While it still votes more Republican than the country on the whole, the margin by which it did so narrowed in 2016 while other districts in the state grew much more Republican. (That includes Democrat Rep. Tim Ryan’s 13th District.)

(Ohio’s 11th, in Cleveland, is not likely to vote Republican anytime this century the way things are going.)

As noted above, West Virginia is the most solidly red of the four states voting Tuesday. Each of the three House districts in the state have shifted strongly to the right in recent years. Cook considers the 3rd District as “likely Republican,” because incumbent Rep. Evan Jenkins (R) decided to try for the Senate nomination in the district.

These are four states in which Republicans can be expected to hold majorities in House delegations after November. What the primaries mark is a transition for those candidates in seats that might be susceptible in November from focusing on appeal to Trump voters to appealing to the electorate broadly. We don’t have figures for each district, but we know that Trump’s approval ratings aren’t great in each of the four states, according to Gallup numbers from January:

  • Indiana: minus-7 net approval (44 percent approve minus 51 percent disapprove)
  • North Carolina: minus-14 net approval
  • Ohio: minus-5 net approval
  • West Virginia: plus-26 net approval

West Virginia is the most supportive state in the nation for Trump. But even there, there’s a district that experts think could switch to the Democrats, despite how much more Republican it is than the country on the whole.

The next six months are going to be strange.