As polls tighten in Republicans’ favor in the final week before the midterm elections, the libertarian vote is becoming an X-factor in close Senate races that could determine the balance of the upper house.

In several swing states — Georgia, Pennsylvania, New Hampshire, Nevada, and Arizona — where the Democrat and Republican candidates are running neck-and-neck, the Libertarian Party candidate is polling high enough to make up the difference.

The GOP should be worried. Traditional wisdom is that Libertarian Party candidates pull more votes from those who would otherwise vote Republican; and, in a year when inflation, government spending, and the fallout from Covid restrictions are at the top of voters’ minds, this adage will likely prove true.

Arizona, though, was crossed off this list on Tuesday. The Libertarian Party candidate for U.S. Senate, Marc Victor, announced he is dropping out of the race and endorsing the Republican, Blake Masters.

“Don’t vote for Marc Victor for Senate. Vote for Blake Masters. Blake’s in a very tight race here with Mark Kelly, and I want to see him win,” Mr. Victor says in a video he released to YouTube.

Mr. Victor was polling between 1 percent and 6 percent support. Mr. Masters is trailing the Democratic incumbent, Mark Kelly, by two points in the latest poll.

The video Mr. Victor released also includes a 20-minute conversation with Mr. Masters, recorded Monday, during which Mr. Victor quizzes Mr. Masters on his positions. The video was part of a precondition for an endorsement that Mr. Victor set earlier this month, when he addressed calls to bow out of the race by extending invitations to Messrs. Kelly and Masters to convince him to do so. On Monday, Mr. Masters accepted.

“I didn’t go into this thinking we were going to get 100 percent agreement on everything,” Mr. Victor tells the Sun. Yet he was impressed by Mr. Masters’ fluency with libertarian thought, from name-dropping Murray Rothbard and Ludwig von Mises to discussing the non-aggression principle. “He has a pretty good understanding of libertarianism,” Mr. Victor says.  

“This is another major boost of momentum as we consolidate our support,” Mr. Masters said in a campaign press release Tuesday. He has actively courted the libertarian vote in recent weeks, tweeting a photograph of himself with Ron Paul and writing that he was “honored” to accept the endorsement of the former presidential candidate and libertarian giant. He also earned the Twitter endorsement of a podcaster and presumptive Libertarian Party 2024 nominee for president, Dave Smith, earlier this month.

“I probably identified as a Libertarian for seven or eight years there,” Mr. Masters says in the taped conversation with Mr. Victor, though he adds the political philosophy works more in theory than in practice. “If you don’t fight back then the left, man, we’ve seen in history where this gets us.”

“Can we count on you to be a ‘live and let live’ senator from Arizona?” Mr. Victor asks.

“Yes, directionally that is where we will go,” Mr. Masters replies.

Several high-profile figures in the Libertarian Party aren’t buying it. “I’m a libertarian, and Masters is an authoritarian grifting as hard as he can to convince both libertarians and nationalists he’s one of them. We disagree on immigration, policing, war, economics, free speech, and more,” a former congressman of Michigan who is a Libertarian Party member, Justin Amash, tweeted.

Don’t expect Libertarian Party candidates in other states to drop out, either. The Libertarian candidate for U.S. Senate from Georgia, Chase Oliver, who is polling at 2 percent support, retweeted Mr. Amash’s condemnation of Mr. Masters, as well as a tweet calling Mr. Victor’s decision to step down “utterly pathetic.” The Democratic incumbent in the race, Raphael Warnock, and the Republican, Herschel Walker, are polling within 3 percent of each other, trading the lead. If neither gets 50 percent of the vote, Georgia law will force a runoff.

New Hampshire’s Libertarian Senate candidate isn’t following Mr. Victor’s lead, either. “I’m not considering dropping out at all,” Libertarian Jeremy Kauffman tells the Sun.

Political pundits have consistently rated the New Hampshire Senate race as “leans Democrat,” but the Republican challenger, Don Bolduc, is steadily gaining ground. A poll released Tuesday shows  for the first time General Bolduc beating the incumbent Democratic senator, Maggie Hassan, by 48 percent to 47 percent. Real Clear Politics just moved the race to a “toss up.” Mr. Kaufman is polling at 2 percent support.

“I’m not here to play a spoiler against someone who’s libertarian. There’s no libertarian in the race,” Mr. Kauffman says. He’s especially critical of General Bolduc’s past comments advocating CIA intervention in Ukraine.

In Pennsylvania, the Libertarian candidate could also help decide the winner. Mehmet Oz is polling ahead of John Fetterman by 2 percentage points in the latest poll. The Libertarian candidate, Erik Gerhardt, is earning as much as 3 percent in polls. 

The Nevada Senate race is also a dead heat. The Libertarian candidate, Neil Scott, is polling between 1 percent and 2 percent, and there are other third-party candidates as well. 

In our highly polarized times, with 62 percent of Americans wanting a viable alternative to the Democrats and Republicans, it’s no wonder Libertarian candidates are polling well enough to cause alarm — even in these tight races. Mr. Victor says he dislikes the spoiler narrative and that voters have to choose between the “lesser of two evils.” Yet he doesn’t have any regrets.

“You can’t please everybody. It’s politics. You can only do what you think is the best thing to do,” he says. “I believe it is in the best interests of freedom and peace to withdraw my candidacy and enthusiastically support Blake Masters.”