Literally one day after winning his primary, Sen. John McCain (R-Ariz.) gave up on Donald Trump. In fact, McCain now sounds a bit like he's betting on Trump losing — or, at least, looking like a loser for the rest of the campaign season — to help him win a sixth term in the Senate.

In a gauzy, five-minute YouTube video released Wednesday, McCain looks directly at the camera and says: "My opponent, Representative Ann Kirkpatrick, is a good person. But if Hillary Clinton is elected president, Arizona will need a senator who will act as a check — not a rubber stamp — for the White House."

In two sentences, McCain is betting that people believe Clinton is going to win in November. And that many voters in Arizona who don't like Trump aren't keen on Clinton either. (A recent national Washington Post-ABC News poll found a record number of Americans dislike Clinton, though she's still more popular than Trump.)

McCain is pulling from a playbook Republicans used two decades ago to ditch the Republican presidential nominee. Before McCain, the highest-profile Republican to deliver that message was House Speaker Paul D. Ryan, who sent a fundraising email in August that read, "If we fail to protect our majority in Congress, we could be handing President Hillary Clinton a blank check." It looked to The Post's Jenna Johnson and Karen Tumulty that Ryan might have predicted Clinton would win in a landslide (because only a historic Clinton landslide would be enough to put the GOP House majority in peril).

Sen. Marco Rubio (R-Fla.), who also won his primary Tuesday, said something similar in June: "I feel deeply that no matter who is elected president of the United States," he told MSNBC, "we're going to need a Senate that has people willing to check and balance that."

Could this work? Maybe. It has before.

Going back to McCain, his strategy is stacked on a lot of "ifs": If Clinton still looks headed for a win in two months. If Arizona voters dislike her enough to elect McCain as a counterweight. If he doesn't upset his GOP base by essentially ditching Trump two months out from the election. If McCain can successfully distance himself from Trump after tepidly sticking by him during the primaries. Kirkpatrick's campaign has no intention of letting voters forget that McCain continued to say he'll vote for Trump after Trump got tangled with the family of a fallen soldier and a million other controversies.

"John McCain has pledged to support Donald Trump over 50 times," the narrator in a recent Kirkpatrick ad says.

It also doesn't leave McCain a lot of room to pivot down the road should the 2016 presidential winds shift in Trump's favor.

Then again, McCain may not have a lot of other options. Campaigning as a bulwark to a President Clinton might be Republicans' life raft in the event of a Democratic wave, just as many Republicans saved themselves 20 years ago — by spending the race's final weeks campaigning as a bulwark against (another) President Clinton. It worked; Clinton won the White House, but Republicans kept their majorities in Congress.

Republicans like McCain think they see the writing on the wall for Trump much earlier — a whole two months before Election Day. Embracing this strategy is a risk — but at this point, one they seem willing to take.