Should Marco Rubio and Ted Cruz say they won't vote for Donald Trump?

Both senators unleashed an almost unprecedented intra-party tirade against the front-runner, but their last debate answers raised doubts about their seriousness.

Are the #NeverTrump folks really serious about the “Never” in their hashtag? And if they’re not, does that blunt the sting of their critiques of Donald Trump?

The conclusion to Thursday night’s Republican debate in Detroit sparks these questions. Their answers could determine just how much a Mr. Trump candidacy would really split the GOP.

Endorsements are the issue here. At the end of the debate Fox host Bret Baier asked Sen. Marco Rubio (R) of Florida, Sen. Ted Cruz (R) of Texas, and Gov. John Kasich (R) of Ohio whether they would support Trump if he wins the nomination. Each answered “yes.”

Senator Rubio said he would back Trump because the Democratic alternative would be either a socialist (Sen. Bernie Sanders (I) of Vermont) or someone under FBI investigation (Hillary Clinton).

Senator Cruz said he would back Trump because earlier in the campaign he’d given his word that he would.

Governor Kasich talked around the issue for a bit and then said “yes” to Trump too.

“Sometimes he makes it a little bit hard, but you know I will support whoever is the Republican nominee for president,” Kasich said.

Here’s the problem: Rubio and Cruz had just spent two hours attacking Trump to an extent seldom if ever seen at the intra-party level. They’d gone after his judgment, his policies, his business legacy, and his demeanor.

Kasich was much less combative. But collectively this trio is the stop-Trump crowd’s best hope. If they had joined in with the spirit of the hashtag, and vowed that they would never vote for Trump, it would have been a serious expression of the depth of feeling of many in the party about the dangers of a Trump nomination.

Rubio in particular has embraced the #NeverTrump theme, including the hashtag in his social media posts and selling #NeverTrump stuff on his campaign website.

But Rubio, and to some extent Cruz, fumbled the moment. If they think Trump is as bad as they were saying during the debate, why not demonstrate the courage of their opposition?

Mitt Romney has. He’s said he will likely write in a third name if his ballot choice is Trump or Mrs. Clinton. (Yeah, yeah, it’ll be “Romney.” Cheap joke.)

A few others in the Republican opposition to Trump have said the same thing. Sen. Ben Sasse (R) of Nebraska has vowed to not vote for Trump. So has former Gov. Christine Todd Whitman (R) of New Jersey.

All the GOP foreign policy experts who signed an open letter opposing Trump also all but said they’d never cast a ballot for The Donald.

If Trump’s remaining GOP opponents had joined this band, it would have brought home how seriously they viewed the situation. Instead, they indicated it was all politics as usual – pro wrestling fake, per New York Times Magazine national correspondent Mark Leibovich.

“Given all the noise and delirium of recent weeks – and some of the things Trump has also said about Cruz and Rubio – this still struck me as a monumental walk-back,” Mr. Leibovich writes.

It’s true that presidential primary campaigns can be very combative. At the end the winner and losers shake hands and are expected to unite for the good of the party. That’s what happened with Hillary Clinton and Barack Obama in 2008.

The 2016 GOP race just seems ... different. Romney and the GOP establishment seem committed to denying Trump a majority of delegates, if possible, and then contesting his nomination on the convention floor.

That could cleave the Republican Party into pieces. Then it would be, as Romney said in his Thursday anti-Trump address in Salt Lake City, “a time for choosing.”