Could libertarians decide the fate of the United States Senate? It’s starting to look that way. For years, analysts have watched the libertarian vote peel away from the Republican Party because of its support of government reach into personal life.

This year, following big Supreme Court decisions, issues like abortion and religion are playing an outsize role in the national debate. So November could be the tipping point and deliver the Senate to Democrats.

A number of observers see control of the Senate as a toss-up this year. FiveThirtyEight and Sabato’s Crystal Ball both say either party could win. Race to the WH gives Democrats a modest edge to retain control of the Senate.

Of the competitive Senate elections, three states — Arizona, Nevada, and New Hampshire — are home to a relatively large proportion of libertarian voters, according to the Cato Institute, a libertarian think tank.

In these states, libertarian-leaning voters can often play kingmaker between Democrats and Republicans. Cato estimates that libertarians and voters sympathetic to the philosophy make up about 15 percent of the electorate in such states.

Libertarian voters in Arizona are fleeing the Republican Party in droves, some political analysts believe, often because of the latter’s hard line on social issues. This flight from the GOP has played a pivotal role in Arizona’s blue shift, the mayor of Tucson, Thomas Volgy,  says.

“As the Republicans move further to the right, what they’ve experienced is substantial flight of libertarians,” Mr. Volgy says. Not necessarily in favor of Democrats, he added, but in favor of independents.

Looking at the issues, the Arizona Libertarian Party identifies “government regulated morality,” “corporate welfare,” “immigration policy,” and “taxpayer funding of faith-based charities” as reasons Republicans lose the libertarian vote.

Such issues are leading libertarian voters, once reliably Republican, to vote for independent or third-party candidates, or even sometimes Democrats, according to the associate editor of Sabato’s Crystal Ball at the University of Virginia Center for Politics, John Coleman.

“You have a lot of libertarian voters who feel politically homeless,” he tells the Sun. “If Republicans make it about a lot of these cultural or religious issues it’s not going to play well with them.”

Mr. Coleman argues that prominent Supreme Court rulings on issues like abortion and the separation of church and state have compounded the libertarian exodus.

“I think those issues — abortion and religion in schools — could play out over multiple election cycles,” Mr. Coleman says. “Longer term, I can definitely see that the Democrats are becoming the more libertarian party, especially on social issues.”

Mr. Coleman predicts that this shift will give Democrats an edge in the House over the long run, and he also gives credence to the notion that libertarians could be the deciding factor in Senate races in states like Nevada, Arizona, and New Hampshire.

He argues that the libertarian vote already delivered one Senate seat to the Democrats, in New Hampshire in 2020.

“Back in 2020, when Jeanne Shaheen was elected, she won by about 15 points, and that’s a blowout by New Hampshire Senate standards,” he says. “That percentage corresponds pretty well with the libertarian vote.”

In national elections, libertarians crossing the aisle “is something that we’ve observed in panel survey data,” the vice president of the Cato Institute, Emily Ekins, tells the Sun.

She notes that many libertarian voters supported Senator Romney in the 2012 presidential election and then voted for Secretary Clinton in 2016. Many more cast their ballots for Governor Johnson in the 2016 presidential election and then supported President Biden in 2020.

This pattern of voting, she argues, is demonstrative of the trends that could lead to Democrats retaining control of the Senate in 2022 with libertarian help. Along with votes in Pennsylvania and Georgia, it is the races in Arizona, Nevada, and New Hampshire that will determine the control of the Senate in 2022.

While the emergence of this voting bloc has largely been under the radar, libertarians themselves predicted it decades ago. In 2006 two analysts at the Cato Institute, David Kirby and David Boaz, argued that Republicans are “going to need to stop scaring libertarian, centrist, and independent voters with their social‐​conservative obsessions and become once again the party of fiscal responsibility.”

“If Republicans can’t win New Hampshire and the Mountain West, they can’t win a national majority,” they wrote. “And they can’t win those states without libertarian votes.”