Karl Rove, an influential Republican strategist, wrote in The Wall Street Journal that President Trump’s political prospects are “more dire” than they were four years ago. “In such a bizarre year, anything is possible. But possible doesn’t mean likely. As insurance, Republicans better fight like hell to keep the Senate.”

Yes, anything is possible. But the idea that Republicans need to focus on the Senate, not the White House, is spreading rapidly. Sort of like a virus. When folks don’t wear masks.

“Republicans on Capitol Hill are beginning to publicly distance themselves from the president,” reports The New York Times. “The shift ... indicates that many Republicans have concluded that Mr. Trump is heading for a loss in November. And they are grasping to save themselves and rushing to re-establish their reputations for a coming struggle for their party’s identity.”

Since the House is virtually certain to remain in Democratic hands, a Trump loss would leave the Senate as the GOP’s only possible outpost of effective power in Washington. But here’s their problem. To “fight like hell” for their majority, as Rove suggests, could mean slighting a president who then explodes at their heresy.

Republican candidates have to tread a very fine line — appealing to moderate swing voters who are backing Biden while not alienating Trump’s hardcore base of fervent acolytes.

“If you’re able to say it out loud, there is an effective message that a Republican Senate can be a check on a Democratic-run Washington,” Brendan Buck, a former top aide to House Republicans, told the Times. “It’s just hard to say that out loud because you have to concede the president is done.”

One critical sign that Republicans are taking Rove’s advice is campaign cash. As Fred Zeidman, a big Republican backer from Texas, said on CNN: “GOP major donors are redirecting money to the Senate races. The Senate is the firewall. We have got to make sure that we hold the Senate no matter who is elected president.”

The battle for the Senate is still very much in doubt. Republicans hold a 53-to-47 edge, and Democrat Doug Jones is facing almost certain defeat in Alabama. So, assuming Trump loses, Democrats need a net gain of four seats in the remaining races to reach 50 and allow Vice President Kamala Harris the opportunity to break ties.

The Economist and the website FiveThirtyEight both give Democrats a three-out-of-four chance of achieving that goal. The Cook Political Report predicts a 51-seat Democratic edge, while Sabato’s Crystal Ball says 52.

But races can be swayed by local — and sudden — surprises. Democratic challenger Cal Cunningham was steadily leading Republican Sen. Thom Tillis in North Carolina until a messy sexting scandal erased his advantage. And it’s entirely possible that Cunningham’s zipper problem could cost the Democrats the majority.

Meanwhile Republicans are grappling with their Trump problem in different ways. Clearly but carefully, Tillis edged away from the president when he told Politico: “The best check on a Biden presidency is for Republicans to have a majority in the Senate. And I do think ‘checks and balances’ does resonate with North Carolina voters.”

Sen. Susan Collins, facing an uphill re-election fight in Maine, urges voters in her latest TV ads to support her “no matter who you’re voting for for president.” Sen. Martha McSally of Arizona, perhaps the most endangered Republican and a former Air Force pilot, declined during a debate to say whether she’d been “proud” to serve under President Trump. “I’m proud that I’m fighting for Arizonans,” she replied.

Republicans who are more comfortably ahead, and less concerned about risking Trump’s wrath, are speaking out more boldly. Sen. John Cornyn of Texas told the Fort Worth Star-Telegram that GOP senators feel “like a lot of women who get married and think they’re going to change their spouse, and that doesn’t usually work out very well.”

But the most outspoken Trump critic has been Sen. Ben Sasse of Nebraska, who said in a town hall what a lot of Republicans will only whisper in private: “What the heck were any of us thinking, that selling a TV-obsessed narcissistic individual to the American people was a good idea?” Sasse, never a big Trump fan added, “I’m now looking at the possibility of a Republican bloodbath in the Senate, and that’s why I’ve never been on the Trump train.”

If Republicans can somehow avoid that bloodbath, and preserve their Senate majority, a President Biden would have a far more difficult time governing the country.

Steven Roberts teaches politics and journalism at George Washington University.