Democrats are on the defensive in a handful of ruby red states a world away from restless, upscale suburbia. It’s territory the president captured in 2016 and that, counter to his very real problems elsewhere, remains quite supportive—of him personally and his nationalist agenda. But Democratic candidates are making Republicans work for it, and G.O.P. insiders are beginning to fret that the party is about to squander an underlying environment in these states that should favor the G.O.P. Still, Democrats would have to draw a Trump-like inside straight to pull off in the Senate what they appear on the brink of doing in the House. A Republican consultant with House and Senate clients explained the unusual atmospherics this way: “The electorate is very engaged this year—probably more than ever before. But their brain is all on Trump. He gets a ton of mental space for every American. That’s good for Democrats in House races, and very good for Republicans in Senate races.”

It’s one of the cruel ironies of midterm-election waves that the first to go are usually the most pragmatic and least responsible for the excesses of the ruling class driving the winds of a change. And so the brewing storm is most likely to cast out of Washington precisely those Republicans most resistant to Trump and his darkest impulses, a changing of the guard hastened by the death of John McCain, the Republican icon who passed away in late August, not to mention a slew of retirements, among them influential figures like House Speaker Paul Ryan. Consider this: if things go right for Republicans in the Senate, the party could see an infusion of new Republican blood precisely because the party’s candidates tethered themselves to Trump (heck, even “Lyin’ Ted” might owe his re-election to his former tormenter). On balance, what was left of the Reagan-era party after Trump’s massive 2016 gut job could be finished off by the voters just two short months from now.

As one House Republican’s chief of staff pointed out, it’s the establishment rank and file that has essentially forced Trump to govern as a “conventional conservative.” Tax cuts, deregulation, banking reform, chipping away at Obamacare, stricter economic sanctions on Russia—these are all priorities of the Ryan-era House. With many of them gone—and with the possibility of a larger, more Trump-friendly majority in the Senate—there will likely be far fewer intraparty restraints on Trump, be it on international trade, attacks on the media, or long-standing norms of governance, both at home and abroad. That means more Republican unity, but on the president’s terms. “If the House flips, Trump will be more of a factor because there will not be a figurehead like Ryan to counter him—and House Republicans will be focused entirely on defending the president against hearings and impeachment, so they’ll be one and the same,” the chief of staff said.

It’s not hard to imagine how the next Congress will quickly reorient itself in relation to Trump. The president is prone to shifting responsibility for failure, and he has “a few knuckleheads around him,” as one knowledgeable Republican described it, that haven’t made clear to him the headache that awaits if Democrats win the chamber. Initially, Trump might figure that he’s better off with a House minority that is at least more unified around his unique leadership. Practically speaking, there’s little else a powerless House G.O.P. minority could do beyond tying themselves to Trump and doing their best to disrupt an avalanche of politically charged investigations. The president might even appreciate this new, more homogenous group. As Trump booster Matt Schlapp, a Republican lobbyist and the organizer of the Conservative Political Action Conference, told me: “If you’re kind of a summertime soldier, and your heart really wasn’t in the Trump agenda, I’m glad they left.”

But that sentiment should evaporate right around the time the first stack of subpoenas from House Democratic committee chairmen arrive in the Oval Office. Even if the Mueller probe has concluded by then, Trump could find himself buried under a bunch of new, mini-Muellers, investigations bursting with insinuations and accusations that at the very least, are likely to be all-consuming inside his head. “If Republicans lose the House, the president will pivot and say it’s not a big deal, and make the case that he won regardless, because he lost fewer seats than past presidents,” the knowledgeable Republican said. “He will not fully understand the incredible headache it will be, in terms of House oversight, but he’ll quickly realize why it’s idiotic not to care.”

David M. Drucker is a senior correspondent for the Washington Examiner and a CNN political analyst.