“These races are like canaries in the coal mine,” Steve Israel, a former New York congressman and chairman of the Democratic Congressional Campaign Committee, told me last week. “For Republicans, the canaries are dying.”

The day before we spoke, Democrats had picked up a statehouse seat in a deep red district in Missouri, the latest in a series of electoral upsets the G.O.P. has suffered across the country in recent months. After a string of special election victories in South Carolina, Montana, and Georgia last spring, the Republican Party has had a reversal of fortune—losing gubernatorial races and dozens of state legislature seats in Virginia and New Jersey, and suffering defeats in traditionally red districts in Florida, Wisconsin, Alabama, Oklahoma, and elsewhere. Ten months out, strategists see the trend as a potential harbinger of the legendary blue wave in the 2018 midterms that could rob of the G.O.P. of its majority in the House—and possibly, the Senate.

For the G.O.P., these midterms are a puzzle box of a kind that they haven’t faced in several cycles, if ever. “Republican consultants in the last eight years have had a very easy job—that’s running against Barack Obama. . . . Now we have to do things differently and nobody is used to it yet,” a G.O.P. strategist, speaking on the condition of anonymity, told me. “That boogeyman is gone.”

And arguably, the new Republican boogeyman is the leader of the party. Since he ascended to the Oval Office, Donald Trump has maintained a vice-like grip on the base of the Republican Party. And yet, while Trump’s popularity has largely proven to be non-transferable, his flagging approval rating—which, despite a recent uptick, is still hovering in the low 40s—augurs suppressed Republican turnout and heightened energy on the left in the midterms.

So Republican candidates are facing an impossible strategic choice, one that is to some degree independent of the president’s approval rating or any economic factor: tack toward Trump, and potentially lose the center, or forgo Trumpian red meat and watch the base stay home. “What you do when you appeal to that 33 percent is you peel off another 50 percent of the voters who will go, ‘Fuck you, I will crawl over broken glass to vote against you because you are a goddamn Donald Trumper,’” Rick Wilson, a G.O.P. strategist and vocal Never Trumper, told me, adding that without Clinton, Trump “has to stand on his own two feet.” And although Trump won’t be on the ballot in 2018, every Republican candidate this fall will be viewed as a Trump proxy. Meanwhile, Democrats will have the luxury of focusing their energy elsewhere. “They get to do that because they’re out of power. That’s a big advantage to them,” the Republican strategist told me. “They let the national environment take care of it and they run on issues that are local and important.”

The G.O.P. challenge is not unlike what Democrats grappled with during the Barack Obama era. “You can approach it by hugging the incumbent president, or you can try to run away from them,” a Florida-based Democratic strategist Steve Schale, who directed Obama’s 2008 campaign in the Sunshine state, told me. “In reality, I am not sure it makes a huge amount of difference—and certainly in 2010 it didn’t.” Of course, the Democratic Party’s electoral success during Obama’s eight years in office certainly doesn’t instill much confidence. The former Illinois senator may have won the White House twice, but Democrats lost more than 1,000 electoral seats under his leadership.