David Becker / Reuters

Better late than never: Like many aphorisms, it’s comforting, but only debatably true. Anti-Trump forces in the Republican Party now have a shot at testing its veracity.

A CNN poll released on Tuesday shows that a stunning 48 percent of Republicans polled would prefer that the party dump Trump in favor of another candidate. The presumptive nominee maintains the thinnest margin of majority support, at 51 percent. Unfortunately, it’s the first time CNN has asked the question, so it’s hard to get a good sense of how that number has changed over time. Trump did win the popular vote in the GOP primary handily, per RealClearPolitics’s count. But he still won only a plurality of the vote, not a majority.

These poll results come amid other bad public-opinion news for Trump, and they fit with the trend. Trump is trailing Hillary Clinton in every recent head-to-head poll, and his unfavorable rating has reached a dismal 70 percent. (Clinton’s own high disapproval is overshadowed.) Trump has had a terrible few weeks, in which he was hammered by Clinton, blundered into an ill-advised attack on Judge Gonzalo Curiel, saw his response to the Orlando massacre panned, and reported next to no fundraising. In short, Trump looks like an incredibly weak presumptive nominee, perhaps among the weakest ever. It makes sense that Republican voters would be losing some faith in him, just as most of the country seems to be doing. For conservatives who warned against Trump, it is bittersweet vindication.

Certainly some Republican officials are edging away. A small but growing number of them have either withheld support, specifically announced they won’t back Trump, or sidled away from him slowly in recent weeks. There’s also a new effort to defeat Trump at the Republican National Convention next month in Cleveland by somehow freeing up delegates to vote for the candidate of their choice. Reaction to this effort, including from me, has tended to be skeptical. After a long series of Stop Trump efforts petered out, or never even got started, it’s hard to imagine one taking hold—especially at this late stage in the game, when Trump has already won the delegates and driven his rivals out of the race. The time to stop Trump was probably long ago.

Nonetheless, The Washington Post reports Tuesday that organizers are now claiming they have nearly 400 delegates on board. That number should probably be viewed skeptically: Who are they? How committed are they? How easily would they swing back? Even if the report is accurate, that number is only about a sixth of the total delegates at the convention.

Meanwhile, Trump seems to be trying to reassure Republicans that he’s righting the ship. On Monday, he fired his controversial campaign manager Corey Lewandowski. On Tuesday, he unleashed a series of emails rebutting a speech by Hillary Clinton—the first such rapid-response effort by Trump’s campaign. On Wednesday, he’s giving a speech criticizing Clinton.

A Stop Trump campaign remains a very long shot. Many things would need to go perfectly for the organizers to succeed, and there would be two essential ingredients for success: a popular groundswell of support, and an alternative candidate. In the CNN poll, Trump’s opponents might see promise in the growing doubts among rank-and-file Republicans. So far, however, they still lack an elite replacement to stand as their figurehead.

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