The Republican candidates and their allies have used every attack they could muster against Donald Trump, from shady business deals to flagrant misogyny, and all their attempts to stop him have failed. Now, with just 80 days and ten primaries left until the Republican Convention, Ted Cruz and John Kasich are resorting to the last possible argument in their favor: that Trump would lose, spectacularly, to Hillary Clinton in the general election, while I (insert candidate’s name) would defeat her.

Both men are doubling down on “electability” in the final days before next week’s Indiana primary, which is shaping up as the last big stand for the #NeverTrump brigade. But they seem blissfully unaware that the strategy is almost certainly doomed to fail—partly because voters are hearing two candidates simultaneously claiming the “most electable” mantle. Cruz and Kasich are not only arguing with Trump about who could win a general election, but with each other.

Early this month, ten days before the New York primary, the Kasich campaign signaled its focus on electability with a new commercial called “One Choice.” “You have only one choice,” the narrator intones, while sepia-toned posters of the other candidates flash across the screen. “One choice that will stop the Clinton political machine: John Kasich.” The Ohio governor has been making the same argument in person—a lot. “I’m the only one who can defeat Hillary Clinton consistently in 15 national polls,” he told John Dickerson on CBS’s Face the Nation this past Sunday. “When we’re at the convention, the delegates are going to want to know who can beat Hillary.”

Cruz is making the same pitch for himself—which involves making the case that he, not Kasich, is the only truly electable option. Shortly before the Associated Press announced Trump had swept all five East Coast primaries on Tuesday, Cruz was telling supporters in Indiana, “Donald Trump is the one man on Earth that Hillary could beat.” His allies at the Club for Growth are using a similar argument in the ads they launched in Indiana this week, while they also take a dig at Kasich. “Only Ted Cruz can beat Donald Trump,” the narrator says in one of the spots, as a disembodied hand scribbles on a chalkboard. “John Kasich can’t do it. The math won’t work.”

On the surface, “he can’t win, but I can” sounds like a pretty compelling argument to make to voters—especially to voters of a party that has lost the last two presidential elections. The Republican rank-and-file desperately want a Republican in the White House, so they ought to support whomever has the best shot at defeating the presumptive Democratic nominee. Right?