Last summer, Donald Trump scared movement conservatives and establishment Republicans—not because they thought that he would actually win the Republican nomination, but because they feared that, in defeat, he would refuse to support the Republican nominee. Back then, it was easy to imagine a general election pitting a Bush against a Clinton—and a third-party bid by an eccentric billionaire throwing the election to Hillary, just as Ross Perot’s bid arguably tipped the 1992 election to Bill.

Trump ultimately assuaged those fears, pledging last September to support the winner of the Republican primary process whether it turned out to be him or one of his rivals. Today, that bet seems smart. Trump appears most likely to be the victor, having won three primaries while maintaining leads in nearly all of the rest. Still, I wonder if it occurred to Trump at the time that the movement conservatives and Republicans who pressed him to forswear a third-party bid made no commitment of their own to support him if he won the nomination. Would conservatives dare to greet a Trump victory with their own third-party challenge?

That once-unthinkable scenario would have to begin with high-profile movement conservatives pledging to break with the Republican Party if it nominates Donald Trump.

Influential pundit Erick Erickson is the latest to do so.

Back in September, he wrote, “I would vote for Donald Trump over John Kasich. But as Kasich will not be the Republican nominee for President, I think it is also worth reiterating that I will vote third party before I’d vote for a ticket that has Kasich as Vice President. A Republican who believes Jesus told him to expand Obamacare is not fit for either the Presidency or to be one heart beat away from the Presidency.”

How times have changed!

Here’s an excerpt from his Monday column, “I Will Not Vote For Trump Ever.”

A lot of Republicans are going to start claiming that we must rally to the nominee, no matter who he is. I know for certain a large number of Trump supporters will not rally to a Cuban. I will not rally to Trump. If Trump is able to get the nomination, the Republican Party will cease to be the party in which I served as an elected official. It will not deserve my support and will not get it if it chooses to nominate a pro-abortion liberal masquerading as a conservative, who preys on nationalistic, tribal tendencies and has an army of white supremacists online as his loudest cheerleaders.

Erickson is hardly alone. Bill Kristol has mused about starting a new political party if Donald Trump wins the Republican nomination. It’s almost impossible to imagine George Will or Kevin Williamson supporting Trump. Glenn Beck declared, “I know that I won't go to the polls. I won't vote for Hillary Clinton and I won't vote for Donald Trump. I just won't. And I know a lot of people that feel that way.”

Here’s Peter Wehner back in January:

Beginning with Ronald Reagan, I have voted Republican in every presidential election since I first became eligible to vote in 1980. I worked in the Reagan and George H. W. Bush administrations and in the White House for George W. Bush as a speechwriter and adviser. I have also worked for Republican presidential campaigns, although not this time around. Despite this history, and in important ways because of it, I will not vote for Donald Trump if he wins the Republican nomination.

Wehner added:

I should add that neither could I vote in good conscience for Hillary Clinton or any of the other Democrats running for president, since they oppose many of the things I have stood for in my career as a conservative — and, in the case of Mrs. Clinton, because I consider her an ethical wreck. If Mr. Trump and Mrs. Clinton were the Republican and Democratic nominees, I would prefer to vote for a responsible third-party alternative; absent that option, I would simply not cast a ballot for president.

Joe Scarborough declared on Morning Joe, “I think Haley Barbour and a lot of the Republican leaders would much rather Hillary Clinton be President of the United States than have Donald Trump represent them as a Republican.” And it is hard to imagine any die-hard Bush loyalists supporting Trump after his attacks on Jeb and George. Indeed, it is easy to imagine them delighting in denying Trump the White House.

Putting them altogether, that’s quite a diverse anti-Trump coalition.  

There are, of course, significant obstacles to an anti-Trump insurgency, like the difficulty of getting on the ballots of many states as an independent. Here’s the blogger Allahpundit injecting additional skeptical analysis:

If conservatives stay home and Trump wins, it’s proof positive that Trumpism is a winner for the new Republican Party — at least until Trump passes from the political scene and a less charismatic character who can’t get on television anytime he or she wants inherits the leadership. Conservatives would be left in the wilderness, roughly where Trump’s white working-class base has been for the past few decades.

If conservatives stay home and Trump loses, what then? They’ll be blamed by Trumpists for his defeat, not unfairly. That rift will run very deep. And even if the rift heals, all sorts of Republican pols and aspiring pols are studying Trump’s playbook right now to see how his coalition might be reassembled in the next few elections. People like to joke that Trump’s success means we’re destined to see many more celebrities run for office, which is probably true but does a disservice to Trump in suggesting that his victories are purely a function of his fame. (They aren’t.)

What we’re certainly going to see more of, though, is Trump-style populist center-right candidacies — protectionist, nationalistic, Jacksonian on foreign policy. Maybe what we’ll find is that the Reagan revolution and the last few years of tea-party orthodoxy were just a phase in which the GOP was transitioning back to an ideologically broader party, a la the days when Nelson Rockefeller and Barry Goldwater were both contenders to land at the top of the ticket, except this new party may be even ideologically messier than the old one. Whatever happens, it’s hard to imagine Trumpists returning to their not-even-a-partner role in the GOP coalition. Why should they, after this year’s success?

Many Republicans may see things that way. But a third-party run does not require unanimity among Trump skeptics. It only requires enough conservatives to launch a campaign. And it seems to me that there are a lot of conservatives who earnestly believe that they have no reason to support a Republican Party headed by Trump. In fact, they’ve spent the last eight years convincing themselves that rebelling against non-conservative Republican candidates is among the noblest of fights.

If a candidate who was clearly more conservative than Trump ran, he or she might attract support even from folks who now feel that a third-party bid is foolish strategy. Other factors that could help bring about such a challenge include the following:

  • In some states, a right-of-center electorate divided between Trump and a conservative challenger could turn out more total voters who’d support down-ballot Republicans than a Trump vs. Clinton race where conservatives stayed home.
  • If Trump wins, there will be a lot of establishment campaign professionals who’d benefit financially from a third-party challenge by a movement conservative (and who wouldn’t fear being branded disloyal for staffing one).
  • Many neoconservatives would prefer an Israel-loving, interventionist hawk like Hillary Clinton to Donald Trump, but also value their place in the conservative movement. Supporting a third-party challenge by a hawkish conservative would be much less disruptive to their network of alliances than openly supporting a hawkish Democrat, even if the likely outcome is the same. A third-party challenger could conceivably draw support both from coy Hillary Clinton Republicans and earnest haters of Clinton and Trump.
  • Right now, we’re seeing Trump in a Republican primary. He is more deferential to the conservative movement now than he would be in a general election—and he’s already breaking with party orthodoxy on health care, entitlements, Planned Parenthood, and foreign policy. I don’t know exactly what he’d say in a general election, but at some point, the faction of the GOP that’s spent 8 years obsessed with ideological purity will rebel. Like Erickson, they'll argue that it’s better to go down fighting as conservatives than to compromise their values. Intransigence is consistent enough with their preexisting beliefs and past behavior to make me believe they’d abandon the GOP for the right candidate.
  • There would appear to be ample money for an anti-Trump third-party challenge. Earlier this month, The Hill reported that the Koch brothers want to stop the billionaire. Last November, it published an article about other GOP donors:

In conversations over the past month, GOP establishment donors have confided to The Hill that for the first time in recent memory, they find themselves contemplating not supporting a Republican nominee for president.  Most, however, still believe that Trump will flame out before they have to face that decision. The subject of Trump came up at a recent Beverly Hills lunch hosted by former U.S. Ambassador to the European Union Rockwell Schnabel. Seated around the table in the private dining room of the Hotel Bel-Air were several of the West Coast's most powerful Republican donors, including Ronald Spogli, the venture capitalist and former ambassador to Italy under President George W. Bush; his business partner Bradford Freeman; and Richard Riordan.  

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In December, GOP campaign veteran Dan Schnur told Politico, “It's impossible to conceive that Republican leaders would simply forfeit their party. Even without the formal party apparatus, they'd need to fly their flag behind an alternative, if only to keep the GOP brand somewhat viable for the future. Otherwise, it would be toxic for a long, long time.” It doesn’t really matter if that assessment is correct or incorrect, so long as enough powerful Republicans feel that it is correct.

I’ll stop short of predicting that a third-party insurgency will ultimately happen.

But it seems obvious that it could deny Trump the White House. And for that reason, the threat of a third-party challenge may be the conservative movement’s strongest piece of leverage over a man who seems to be thwarting them at every turn. As long as Marco Rubio or Ted Cruz could still win the nomination, a third-party plot might cause Trump to reverse his own loyalty pledge in the event he loses. But if and when Trump has the nomination clinched, I expect, at the very least, that movement conservatives will make a lot of noise about a third-party challenge. It may be their last best chance to wrest concessions from the billionaire.