When Bill Weld, the former Republican governor of Massachusetts, decided to join Gary Johnson’s campaign for the presidency, it seemed plausible that the Johnson–Weld ticket could garner 9 or 10 percent of the vote against two widely disliked alternatives. Weld had been a respected, moderate governor, and was seen as giving the somewhat eccentric Libertarian Party a dose of gravitas. But things haven’t worked out that way: Johnson has become a national punchline after displaying an inability to identify the Syrian city of Aleppo and doing little to complicate the image of the pot-smoking, Ayn Rand–reading libertarian that Americans enjoy rolling their eyes at.

Unlike Johnson, who has been a pointed critic of Hillary Clinton, Weld seems genuinely frightened at the prospect of a Trump presidency. He has attacked Trump harshly and said he would focus his energies on going after the demagogue. He has also called Hillary Clinton as qualified as anyone to be president. Which raises the question: Why exactly is Weld supporting Johnson’s bid for the presidency, which could conceivably cost Clinton the election if polls tighten? I called Weld to ask. During the course of our conversation, which has been edited and condensed for clarity, we discussed what Republicans really think of Trump, Gary Johnson’s fitness to be commander in chief, and Weld’s advice for swing-state voters.

Isaac Chotiner: Why are you running as vice president on the Libertarian ticket?

Bill Weld: I have always self-identified as a small-l libertarian, and I was very friendly with Gary Johnson when we served together as governors back in the 1990s. So when he called and said, “Would you like to consider being on the ticket?” it was not a very difficult decision for me. I have long been interested in national politics. I was Pete Wilson’s national finance chair. I was Mitt Romney’s New York finance co-chair twice. I have been familiar with all the players for 20-plus years. It’s been a great ride.

OK, but why do you want to be elected vice president, and why do you want people to vote for the Libertarian ticket?

Oh, because the Libertarian platform is my platform, and neither of the other party’s is. I have run as a Republican many times, but I always carried the Republican Party position on social issues on my back as a 300-pound monkey. I never agreed with the social issues approach of the Republican Party. And it has only gotten worse. Now they want gays and lesbians to have conversion therapy. I was out there for a decade by myself in the 1990s on gay and lesbian civil-rights issues, and people said, “What are you, crazy?” I am not crazy, I just know what I think. I’m a real libertarian on social issues and I am very much a small-government conservative on fiscal issues. It is a perfect fit. I would not say the Democratic Party is small-government conservative these days. [Laughs.]

You have spent a lot of your time going after Donald Trump recently—

Well that’s right. I have been watching him closely and the campaign closely and I think it has just gotten worse and worse. When anybody confronts him or criticizes him, he behaves as a small child would. His face turns red, he waves his arms, he interrupts everybody, he stands on one leg and holds his breath until he gets what he wants. You can’t do that if you are the president of the United States.

Does the descent of the Republican Party and Trump make you think differently about third parties?

Well, yes. I think the Republican Party at their convention decided to make their platform even more mean-spirited than it already was. Both parties have gotten somewhat less appealing because of the hyperpartisanship in Washington, which is itself a product of hypergerrymandering and the fact that the two parties want to kill each other. That’s no way to get the people’s business done.

If I were a socially liberal, capitalist-friendly person, Hillary Clinton wouldn’t seem so bad. Where do you disagree with her?

Well, I do think that one of the big issues in this year’s campaign—and I wouldn’t call it the elephant in the room, I would call it the elephant and the donkey in the room—is the fact that the two-party monopoly in Washington has begun to be quite counterproductive. All anyone is worried about is getting re-elected. The only silver bullet I can see for that is term limits.

If you don’t—

Excuse me. Excuse me. Let me just finish. The exception to that is if a credible third party has a seat at the table at the national political dialogue. That would make the other parties have to be more honest.

I am sure you have heard the argument that if you have term limits, you don’t have expertise and so lobbyists and special interests actually have more power.

Yeah. I am not buying that for a minute.

What I am wondering about your ticket is whether you want Gary Johnson to be president or rather that you think the Libertarian Party has the right ideas and we need to give people a choice.

Well it’s certainly the latter, and I think Gary would be a good president. He was a good strong governor of New Mexico and I think he’d be a good, strong president. I don’t get off the bus just because Gary [forgot] a place name in Syria on national television. He worked across the aisle when he was governor.

You say it’s a place name in Syria, but he doesn’t seem like someone who has thought deeply about foreign policy. Is that wrong?

I think it is fair to say that I have had the occasion to travel a lot more widely than he has. It’s partly because I was an Eastern governor. It’s partly because my business and consulting practice has taken me all over the world. I think it is fair to say that Gary and I have influenced each other this year, just as good friends traveling a lot and talking a lot. One of the areas where I have had some impact on his thinking is in terms of constructive engagement around the world. But he was already in favor or military and naval supremacy. I’m sorry, naval and air power as a defensive matter.

Sorry, he was always in favor of naval and air power?

Wait, wait wait wait. Let me finish. And he has had some impact on me in terms of criminal justice reform, for example mandatory minimum sentencing and treating addiction matters as a health issue rather than a criminal justice issue.

Sorry, he was always in favor of naval and air power? What does that mean?

Military supremacy in naval and air power.

I just don’t know what that means. American supremacy?

Right, and have that be demonstrable all over the world. And that is a result of our discussion. So he is on board for having the United States maintain military supremacy in naval power and air power, while at the same time, he is more skeptical about boots on the ground than perhaps either of the other parties.

It seems harder to make the case against Trump when Johnson, like Trump, gives off the vibe of someone who does not think deeply about foreign policy and might not necessarily be ready to be commander in chief on Day 1.

OK, well that’s your point of view. I think Gary Johnson could be commander in chief.

Is your sense from talking to Republicans you know that they want Trump to be president—or that they don’t and just want this period to be over?

Oh I don’t think they want Donald Trump to be president at all, but that’s why I am flabbergasted that so many of them are standing around catching flies, meaning with open mouth, while this election proceeds. And I think there is a decent chance Donald Trump could win the thing. I think there is a hidden Trump vote of 3–4–5 percent of people who just don’t want to admit to a pollster that they are going to vote for Donald Trump. I don’t know if you saw the statement I put out yesterday but I addressed it squarely toward Republicans who are standing by while the Trump train chugs on. That’s why my remarks were about Donald Trump and not anybody else. I wanted to focus people’s attention on this before we do ourselves some lasting harm, and I think the election of Donald Trump would constitute lasting harm.

I don’t know if I agree with you about the hidden Trump vote but—

I hope I am wrong.

I hope you are wrong too. I just don’t know how you tell people in swing states to vote for you and Gary Johnson instead of Hillary Clinton if that’s the case.

[Nine second pause.] Is that a question?

Take it for—

I see your point of view. You know, I stand by what I said about Libertarians getting a seat at the table of the national political dialogue going forward would be very good for the country. I think the two-party duopoly has become sick.

Well, if Trump is elected we won’t have a two-party duopoly but instead a one-party state.

I completely agree.

Correction, Oct. 26, 2016: Due to a production error, an earlier version of this article was published under the wrong byline and with several paragraphs missing. The missing text has been added, and the byline has been updated.

Read more Slate coverage of the 2016 campaign.