In the 2014 midterms, only 36.7 percent of eligible voters turned out to vote. That compares to 58.6 percent of eligible voters who turned out for the presidential election in 2012 and 62.2 percent who turned out in 2008.

We can learn several things from just these numbers. First, obviously there can be some significant variation in presidential turnout depending on how interested and enthusiastic voters are and how well the campaigns do in dragging their supporters to the polls. The drop-off in turnout from 2008 to 2012 was probably attributable almost entirely to diminished enthusiasm on the left, although there are theories out there that Romney didn’t get out the Republican base as well as McCain had four years earlier. Maybe some people didn’t like the idea of a Mormon president, and others weren’t sold on a Bain Capital vulture capitalist.

Still, even a relatively low turnout presidential election dwarfs a midterm election where no president is on the top of the ticket. There’s a twenty-five point drop in the percentage of people who voted in 2014 compared to 2008. And, among that group of people, most are assuredly not going to show up to vote for a Republican congressman if they first determine that they can’t support Trump. They’ll show up to vote for the president. If they can’t support anyone for president, then they will not show up.

Of course, there’s another group of people who always show up to vote and always vote Republican. Among these folks, yes, there will be strategic ticket-splitting, with many voting for Clinton or Libertarian Gary Johnson, and then casting their support behind down-ticket Republicans as a check on Clinton’s power. For this reason, Clinton will probably outperform non-incumbent Democratic congressional candidates in swingy districts and states.

Yet, the Republicans are right to be concerned about preserving their House majority.

“Our biggest concern would be that they would choose to stay home because they are so disgusted with both people at the top of the ticket,” said Mike Shields, the president of the Congressional Leadership Fund, a super PAC that backs Republicans. “If they show up, then I think we’re in very good shape.”

Mr. Shields’s group last week announced the first wave of a $10 million spending plan, emphasizing more diverse and affluent districts.

As you can see, Mr. Shields is in the uncomfortable position of wanting disgruntled Republicans to show up and cast a vote for Clinton rather than staying home in protest of Trump.

But here’s another not-too-secret fact. One of the best ways to suppress turnout is to wage an ugly, divisive campaign that makes people disgusted by and ashamed of our political system. When folks turn away from the campaign in horror, they’re much less likely to get involved or to cast their ballot. Clinton can try to take the high road, but whether you call that a run out the clock strategy or not, it’s a risky proposition to let vicious attacks go unanswered. If you doubt me, just ask John Kerry.

The uglier the Republicans get with Clinton, the fewer soft Republicans will turn out to vote for her and the more soft voters will decide to shield their children’s eyes from the teevee rather than use the campaign as a proud opportunity to teach them a civics lesson. Clinton will shed support in this process, but probably not enough to matter. And much of the support she loses will be lost votes for down-ticket Republican candidates, too.

For local, state, and federal Republicans, they want their people to show up, and if they won’t vote for Trump and they’ve been persuaded not to vote for Clinton, that’s simply not going to happen in the numbers they need.

These excruciating conundrums are playing out in weird ways all over the country. For example, John McCain was mocked by Trump for getting captured by the North Vietnamese, a fact that is still haunting him. McCain knows that he’ll lose if Trump’s supporters consider him the enemy, so he’s doing everything he can to avoid provoking them. But his tepid support of Trump is so emasculating and unconvincing that it’s destroying his unearned reputation for honesty as well as the credit he gets for his well-known courage. Now try to imagine how he can do that dance while simultaneously trying to tap out a tune for disenchanted Republican base Clinton voters!

Thus, Republican candidates are getting whip-sawed by conflicting and irreconcilable imperatives.

Mr. Trump’s unpopularity, which has already undermined the party’s grip on the Senate, now threatens to imperil Republican lawmakers even in traditionally conservative districts, according to strategists and officials in both parties involved in the fight for control of the House.

Democrats are particularly enticed by Mr. Trump’s dwindling support in affluent suburban areas — including those near Kansas City, Kan.; San Diego; Orlando, Fla.; and Minneapolis — where Republicans ordinarily win with ease. Mr. Trump is so disliked among college-educated voters, especially white women, that he is at risk of losing by double digits in several districts that the 2012 Republican nominee, Mitt Romney, carried comfortably.

You can add a lot of other places to that list, like Northern Virginia, the Philly suburbs, and perhaps to a lesser degree the suburbs around key cities like Atlanta and Cleveland. In North Carolina, the unpopular governor and Republican state legislature are only adding to the woes.

It’s too early to tell how things will shake-out, but I’ll tell you one thing. The day before the 2014 midterms, no one was predicting that Republican Larry Hogan would be elected as governor of Maryland, and few foresaw that Charlie Baker would become the governor of Massachusetts. When a wave hits, it’s very hard to predict how for up the shore it will go and much beach erosion it will cause. The warning signs are already here for the Republican House. The lack of any professional organizing from the Trump campaign assures that Republican votes will get left on the table, and the GOP can’t figure out how to attack Clinton without inadvertently dropping an anvil on their own feet.

There are no answers for this. The only solution was to not nominate Trump in the first place.