When Roy Moore unexpectedly lost the Alabama special election just a month after Democrat Ralph Northam triumphed in Virginia, Democrats emerged from their burrows to sniff hopefully at the air. Pundits proffered dire predictions of a Democratic wave in 2018, warning that Moore, despite the messy scandal he embodied, was not an outlier.

So following the surprise resignation of Pennsylvania Rep. Tim Murphy, the White House seems to have decided that there is no such thing as overcompensation. In the next few weeks, Donald Trump will visit the district, as well as Vice President Mike Pence and several Cabinet members, to campaign on behalf of Rick Saccone, their preferred replacement candidate. Their outside allies in the R.N.C., the N.R.C.C., and the smattering of PACs in conservative donor world, plan on spending over a million dollars in the district—a district, it should be said, that Trump won by 20 points. “It should go Republican,” G.O.P. Congressman Charlie Dent told Politico, “but in this environment, one can never take anything for granted.”

Both Murphy and Dent belong to the growing group of Republicans who will vacate their seats for a bevy of reasons, potentially throwing G.O.P. control of the House into jeopardy. Their number swelled to 31 on Wednesday, when veteran representative Darrell Issa announced that he would not seek re-election. Most are leaving for reasons similar to Issa’s: the powerful congressman barely won re-election in 2016, and saw his Orange County district tilt alarmingly in Hillary Clinton’s favor. And one, Trent Franks, was swept up in the recent sexual harassment dragnet, forced to resign after allegations of inappropriate behavior toward female staffers.

But in one way or another, all face the political reality of belonging to a wildly unpopular party, led by the most unpopular president in the modern era. Worse, they face an energized grassroots Democrat electorate, which has so far turned races for even surefire Republican seats into contests that are uncomfortably close. Meanwhile, talk of a Democratic resurgence has reached a fever pitch: “You can't really look at tonight’s results and conclude that Democrats are anything other than the current favorites to pick up the U.S. House in 2018,” tweeted Dave Wasserman, the House editor for the nonpartisan Cook Political Report, after Northam’s win.

For the G.O.P., it remains maddeningly unclear how the White House, and the Republican party at large, will respond to the exodus. The administration’s political office, which is overseen by Bill Stepien, recently underwent a shake-up to address last year’s legislative and political failures. But insiders have suggested that the organization is still hopelessly directionless, and that “nobody knows what the f--- [Stepien has] done or is doing to advance the president’s agenda politically.” (Politico implied that the Trump White House only understood the grave importance of the Pennsylvania race after House Majority Leader Kevin McCarthy made a presentation about it during a party huddle at Camp David last week.) As such, Republicans may be right to pour undue resources into a House race they’d normally take for granted—should they lose the election, they may be helpless to stop the ensuing tide of fleeing congressmen.