Political free spirit Bill Weld, the former Republican governor of Massachusetts who ran for vice president on the Libertarian ticket in 2016, is embarking on his most quixotic mission yet: challenging Donald Trump in the Republican primary. “I cannot sit quietly on the sidelines any longer,” he declared at the “Politics & Eggs” breakfast in New Hampshire on Friday morning, announcing his intention to form an exploratory committee to run for president.

Weld laid out a fairly traditional Republican platform—cut spending, implement flat taxes, etc.—but made it clear that his primary goal is getting in Trump’s head. “Our president is simply too unstable to carry out the duties of the highest executive office,” he said, calling out Republicans as victims of “Stockholm syndrome.” Weld was unsparing: “The truth is that we have wasted an enormous amount of time by humoring this president, indulging him in his narcissism and his compulsive, irrational behaviors.”

Matt Welch, the former editor-in-chief of the libertarian Reason magazine, who was at the breakfast event on Friday, told me that Weld knows it’s a long shot. But Weld has also studied recent presidential history, and knows that incumbents who face primary challengers typically lose. “He’s clearly trying to derail Trump, as much as anything else,” explained Welch, who has followed Weld for several years as a reporter. “But then, it’s also a bet,” he continued. “Who the hell knows what’s going to happen with the Mueller investigation or with Trump himself. So someone’s gotta be left standing, competing. So part of this, I think, is either he’ll be the last guy standing, the only one who’s foolish or brave enough to compete—or, by his example, other people who’ve been on the sidelines will now jump in.”

Could Weld be the game-changing candidate who breaks the dam? Several other Republicans have been mulling runs, including popular Maryland Governor Larry Hogan and former Ohio governor John Kasich. Never Trumper operatives have signaled that should a challenger arise, there’s a campaign apparatus in wait, donors and organizers and all.

Of course, there are also substantial barriers to entry. The Trump-aligned G.O.P. has been taking measures to prevent any such challenge. The Republican National Committee has already taken steps to cull disloyal party members. At least one member of the R.N.C. has pushed to change party rules that currently make it easy for a well-funded challenger to get a vote on the convention floor. And just in case any delegates get any funny ideas about standing up for their principles, the Trump campaign has begun meddling in state and local party elections to get reliably pro-Trump delegates into the convention. (As Trump’s own senior campaign adviser Bill Stepien told the Associated Press, “the national convention is a television commercial for the president for an audience of 300 million, and not an internal fight.”)

But given the strange makeup of several state primaries—New Hampshire, for instance, has an open primary that allows independents to vote—as well as polls suggesting that Republican voters would welcome a robust primary challenger, Weld might at least be able to cause the president some pain.

The biggest complicating factor is probably Weld himself. “He’s not charismatic enough, if we’re being honest,” said Welch. “Not to say he doesn’t have personality, he does, he’s a very interesting, polished guy. But in the way that’s going to make someone’s knees tremble with excitement in Iowa, that’s just not part of the package.” His support for abortion rights and marijuana legalization is also likely disqualifying for Trump-skeptical conservatives. At the same time, Weld clearly has no interest in running as a Democrat. “We need the opposite of socialism,” he said Friday, echoing Howard Schultz, another long-shot contender for the White House who is plainly terrified by the Alexandria Ocasio-Cortez-ification of the left.

That doesn’t leave Weld with much of a constituency, or a viable pathway outside of New Hampshire. But, as Welch says, “Anything is possible.” “You know, you’ve got a hundred to one odds for Trump back in the day. . . . So part of it is, hey, why not. Crazier things have happened so I’m going to jump in.”

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