This is how a political party looks when it’s coming unglued.

Last week, the Republicans’ two most recent presidential candidates, Mitt Romney and John McCain, denounced this year’s likely nominee, Donald Trump.

“Donald Trump is phony, a fraud,” Romney said. “His promises are as worthless as a degree from Trump University.”

McCain piled on, warning that Trump’s views on foreign policy were “dangerous.”

Dozens of other Republicans, including a conservative U.S. senator, declared that they would not vote for Trump if he becomes the nominee.

And Thursday night’s televised debate among the candidates degenerated -- again -- into a shouting match of schoolyard insults.

This from a party that likes to thinks of itself not only as the natural party of government, but as the party of ideas and family values.

Romney and McCain are right, of course. Trump isn’t just divisive and vulgar; with his anti-constitutional impulses on foreign policy and law enforcement, he’s a danger to the country. His election as president would be a disaster, and not only for the GOP.

So leaders of the establishment have concocted a plan to fight back -- which will almost certainly fail.

“This is a time for choosing,” Romney said, quoting Ronald Reagan. But Romney didn’t actually make a choice. Instead, he offered a multiple-choice endorsement.

“Given the current delegation selection process, that means I’d vote for Marco Rubio in Florida and for John Kasich in Ohio and for Ted Cruz or whichever one of the other two contenders has the best chance of beating Mr. Trump in a given state,” Romney said.

The aim, in other words, isn’t to crown a single establishment favorite. It’s merely to deny Trump a majority of delegates before the July convention in Cleveland -- and then let the convention decide, the way conventions did a century ago.

This last minute appeal isn’t likely to work for two reasons.

First, it won’t reduce Trump’s strength in the primaries much. It might even bolster it.

Many of the Trump voters who have pushed primary turnout to record levels are new voters, people who never saw much to like in Republican candidates before this year.

“Trump has brought out thousands of people we’ve never seen before,” one GOP operative told me.

In an NBC News exit poll, 85 percent of Trump’s voters in primaries on March 1 said they wanted a nominee from “outside the establishment.” Those people aren’t looking for advice from Romney or McCain.

Second, the establishment strategy is too complicated. If it’s to work, anti-Trump voters have to band together and vote for a different candidate in each state: Rubio in Florida, Kasich in Ohio and Cruz in North Carolina. Got that, everybody? Convincing social conservatives in Ohio to switch from Cruz to Kasich, or moderate Republicans in North Carolina to vote for Cruz, is a tough ask.

Plus there are only nine days to get the message out. Ohio and Florida vote on March 15. If Trump wins both (he’s ahead in the recent polls, although his lead in Ohio is narrow), the race will effectively be over.

To summon the inevitable sports metaphor, the establishment’s “fragmentation” strategy is a Hail Mary pass. As every football fan knows, Hail Mary passes are thrilling to watch, but they rarely produce touchdowns.

Sorry, GOP: You waited way too long to build an anti-Trump majority. Unless a miracle happens, you’re about to get knocked out by an anti-establishment wave -- a wave you mistakenly encouraged in the first place.

By comparison, Trump’s strategy is pretty coherent. He‘s already built a coalition of white working class voters, disgruntled moderates and “soft” evangelicals (the ones who don’t care how many times the candidate has been married).

His pluralities have generally become larger, not smaller, as other candidates have dropped out. Trump won the first primary in New Hampshire with 35 percent; last week, he won Georgia with 39 percent and Massachusetts -- Massachusetts! -- with 49 percent.

Establishment strategists figure the remaining primaries will be harder for Trump, since they’re open only to registered Republicans (unlike, say, New Hampshire, where independents can join in).

But even their best-case scenario concedes that Trump is likely to arrive in Cleveland with more delegates than anyone else. At that point, someone, somehow, will try to arrange a deal -- among delegates pledged to candidates as varied as Cruz and Kasich, remember -- to create a majority around a single anti-Trump figure. At which point that huge bloc of Trump delegates does what, exactly?

The only guarantee is chaos.

Trump could still win the nomination, prompting more boycotts by traditional Republicans. Or, less likely, the establishment could deny the front-runner a prize he thinks he won fair and square -- prompting an independent Trump campaign.

Either way, there’s already one winner: the Democratic candidate -- who is almost certainly going to be Hillary Clinton.

There’s no exact historical analogy to the civil war in the GOP, but we’ve seen major parties fracture in the past. In 1968 and 1972, Democrats divided bitterly over the Vietnam War. In 1964, Barry Goldwater’s conservative insurgency split Republicans. Or go all the way back to 1912, when Theodore Roosevelt bolted from the GOP.

Notice a pattern? The party that divided lost the presidential election every time.

By Doyle McManus

Doyle McManus is a columnist for the Los Angeles Times. Readers may send him email at doyle.mcmanus@latimes.com. -- Ed.

(Los Angeles Times/Tribune Content Agency)