In rallying disaffected Republicans and independents, Donald Trump has identified a set of internal contradictions in the G.O.P. that the Party can no longer conceal. Photograph by Thos Robinson / Getty

Give one thing to the organizers of the Republican effort to stop Donald Trump from getting the G.O.P. nomination: they know how to make a negative ad. The sixty-second spot about Trump University that the Our Principles super PAC started airing on Wednesday is devastating. It alternates clips of Trump promoting the so-called school, which he launched in 2005, with accusations from the office of Eric T. Schneiderman, New York's Attorney General, that it was a scam operation that bilked each student out of as much as thirty-five thousand dollars. After watching the spot, you are forced to wonder why on earth the Bush, Rubio, and Cruz campaigns didn't put out something like it six months ago.

That's a question for the campaign historians to answer. The immediate question is whether the “Never Trump” movement can succeed. For at least a couple of reasons, I am deeply skeptical.

The first goes to the old saying that you can't beat something with nothing. The dump-Trump movement has a clear and convincing message—he's a dangerous charlatan—but it doesn't have a candidate. Some of the people behind the Our Principles PAC, such as the hedge-fund billionaire Paul Singer, are supporters of Marco Rubio, but Rubio's campaign is sagging badly. Over the next six days, another nine Republican primaries or caucuses will be held, and the Florida Senator isn't favored to win any of them, except perhaps Puerto Rico. According to the polls, he's also well behind Trump in his own state, which votes on March 15th.

That leaves Ted Cruz, who will be looking to follow his three wins on Super Tuesday with a victory in the Kansas caucus, on Saturday. Elsewhere, however, Cruz's prospects don't appear to be good. His extremism on social issues turns off many moderates and independents, and he hasn't done well in the northern states that have voted so far. Plus, he has alienated other elected Republicans in Washington to such an extent that many of them would rather take their chances with Trump.

Who else is there? Some cynical folks believe that Mitt Romney, who gave a Trump-bashing speech, in Salt Lake City, on Thursday, is trying to position himself as the Republican Party's savior. Come the convention, this theory goes, it’s possible that no single candidate will have a lock on the nomination, and the Republicans may be forced to turn to a unifying figure like the Mittster.

When you stop laughing, I'll move on to the second reason I doubt Trump can be stopped. In rallying disaffected Republicans and independents, he has identified a set of internal contradictions in the G.O.P. that no amount of negative advertising can conceal. And rolling out somebody like Romney only highlights these contradictions.

For decades now, the Republican Party has been appealing to low-income and middle-income whites while promoting an economic agenda that runs contrary to their interests: tax cuts for the rich, deregulation, free trade, deep cuts to entitlement programs, and so on. Trump, who is hawking a tax plan that he appears to have ordered up at short notice from Art Laffer or Larry Kudlow, can be accused of adopting the same bait-and-switch tactics, but taxes aren't central to his campaign. In promising to end illegal immigration and impose hefty tariffs on good from countries like China and Mexico, he can, at least, claim to be pursuing an agenda that would boost American wages and save American jobs.

Would his strategy work? Probably not. But in talking about safeguarding Social Security, forcing pharmaceutical companies to lower their prices, preventing people who don't have health insurance from dying in the streets, and eliminating tax breaks that favor hedge-fund and private-equity managers (such as Romney), Trump is using the language of economic populism in a manner that none of his Republican rivals can match. Beholden to their campaigns backers, they are forced to confine themselves to the standard guff about cutting taxes, loosening regulations, and encouraging enterprise. At this late stage, many none-too-affluent G.O.P. voters appear to be smelling a rat.

In the past, Republicans cleverly obfuscated the regressive nature of their economic platform by appealing to social issues, and quietly playing the racism/xenophobia card. Trump, however, is beating his rivals at this game, too. On social issues, he has demonstrated that you don't have to be a Bible-thumping pro-lifer to attract the vote of evangelicals. On immigration, by promising to round up and send home eleven million undocumented workers, he has trumped even the Cruz wing of the G.O.P. And in playing to white hate groups and other racists he is doing what other Republicans, particularly in the Deep South, have been doing for generations. But, while many of these Party regulars used a dog whistle, Trump is using a foghorn.

In the conservative intellectual world, there are people with a clear view of what is happening. "More than anything else, Trump has demonstrated that white working-class voters have minds of their own," Reihan Salam, the executive editor of National Review, wrote in Slate earlier this week. "Why wouldn’t they be furious? The Republican failure to defend the interests of working-class voters, and to speak to their hopes and fears, has made Trump’s authoritarianism dangerously alluring." Salam went on, "There is only one way forward in the post-Trump era. The GOP can no longer survive as the party of tax cuts for the rich. It must reinvent itself as the champion of America’s working- and middle-class families."

Good luck with one, Reihan. To follow the program he and other reformicons have laid out, the Republican Party would have to accept that the Affordable Care Act is here to stay; extend tax credits for low-income households; offer workers "wage insurance" against the possibility of losing their jobs; invest more in public infrastructure; and vow not to introduce any further tax cuts for households earning two hundred and fifty thousand dollars or more. In short, the G.O.P. would have to move beyond Reaganomics, ditching the pretense that tax cuts and an untethered free market will produce enduring prosperity for ordinary Americans.

Perhaps I missed it, but I didn't see anything along these lines at the Our Principles PAC’s Web site, or in Romney's speech (which my colleague Amy Davidson wrote about), or in anything anybody associated with the stop-Trump movement has said over the past few days. As New York magazine's Jonathan Chait commented on Twitter on Thursday, "#NeverTrump, at its core, is people satisfied that the Republican Party is fundamentally sound." And that, in the final analysis, is why they are unlikely to be able to see off Trump's insurgency.