When Tarie MacMillan switched on her television in August to watch the first Republican presidential debate, she expected to decide which candidate to support.

But MacMillan, a 65-year-old Florida resident, was disappointed. “I looked at the stage and there was nobody out there who I really liked. It just seemed like a showcase for Trump and his ridiculous comments,” she recalled. “It was laughable, and scary, and a real turning point.”

So she decided to back Bernie Sanders, the self-described “Democratic socialist” challenging Hillary Clinton. MacMillan was a lifelong Republican voter until a few weeks ago when she switched her party affiliation to support the Vermont senator in the primary.  It will be the first time she’s ever voted for a Democrat.

That story may sound improbable, but MacMillan isn’t the only longtime conservative supporting Sanders. There are Facebook groups and Reddit forums devoted entirely to Republicans who adore the Vermont senator.

These Republicans for Sanders defy neat categorization. Some are fed up with the status quo in Washington, and believe that Sanders, with his fiery populist message, is the presidential contender most likely to disrupt it. Others have voted Republican for years, but feel alarmed by what they see as the sharp right turn the party has taken.

“I have been a conservative Republican my entire life. But the Republican party as a whole has gotten so far out of touch with the American people,” says Bryan Brown, a 47-year-old Oregon resident. “I switched my registration so that I could vote for Sanders in the primary, but the day the primary is over I’m going to register as an Independent.”

Anger and alienation have turned conventional wisdom upside down in this presidential election. Self-styled outsider candidates like Donald Trump and Ben Carson have surged in the polls. And as Republican candidates debate their conservative credentials, support for Sanders shows how difficult it can be to pin down what exactly it means to be conservative.

“Once you get out of Washington ‘conservative’ can mean all sorts of different things. Voters are often left of center on some issues and right of center on others. So someone like Trump or Sanders who talks about themselves in a way that doesn’t fit into a pre-ordained box could be appealing to a lot of people,” says Chris Ellis, a political science professor at Bucknell University.

In some cases, longtime Republican voters who have decided to support Sanders, like MacMillan, are rethinking their political affiliation entirely. (“I’m inclined to say I might stay with the Democratic Party because the Republican Party has changed and it’s not the way it used to be,” MacMillan says.) Far from claiming to have experienced a political conversion, other Republicans argue that Sanders actually embodies conservative values.

“When I think of true conservative values I think of Teddy Roosevelt who earned a reputation as a trust-buster,” says Jeff DeFelice, a 38-year-old registered Republican voter living in Florida.Now look at Bernie. He’s the only one willing to stand up to the big banks. The big banks control an obscene amount of wealth in this country and he wants to go after them.” If Sanders looks like “a viable candidate” by the time the primary rolls around, DeFelice says he’ll switch his party affiliation to vote for the senator.

Sanders’s promise to wrest power away from Wall Street and return it to the American middle class taps into the same vein of populist anger that fueled the rise of the Tea Party. It’s also a message that resonates with mainstream Republicans and Democrats. Sixty-two percent of Republicans, for example, believe that large corporations wield too much influence on American politics, according to a New York Times/CBS News poll conducted in May.

“Sanders has focused primarily on economic issues on which Americans are not divided,” says Elizabeth Coggins, a professor at Colorado College who studies American political psychology and ideological identification. “There is a strong consensus in agreement with Sanders on many of his core ideas, and his rhetoric has been largely centered on these sorts of issues.”

It’s difficult to say how deep conservative support for the senator runs. But its existence nevertheless challenges the notion that Sanders won’t be capable of building a diverse coalition to back his campaign during the 2016 presidential contest.

Still, some of the stands that may make Sanders attractive to conservatives leave a bad taste in the mouths of many liberals. Sanders brags about his D- rating from the National Rifle Association, but has suggested in the past that gun laws are best left to the states. “I’ve always felt like most issues should be handled on a state level, and he kind of takes a state level approach to gun control,” says Ashby Edwards, a 43-year-old self-described lifelong conservative living in Virginia.

Other Republicans are drawn to his fiery personality: “I’ve watched some of Bernie Sanders’s town halls and there have been people who will try to speak over him and sometimes he just tells people to shut up and starts screaming at them. That’s awesome,” says Andrew Holl, a 38-year-old registered Republican voter living in Florida. “I think it’s evidence of being genuine. He reacts honestly in every situation.”

Holl plans to vote for Sanders if he makes it to the general election.  “This is the first time I’ve ever considered voting for a Democrat. If you read the definition of what a Republican is and what those ideals are that’s me. But when you look at the Republicans in this election, I don’t like most of them,” Holl adds.

Some conservatives readily admit they don’t love everything Sanders stands for, but insist that doesn’t change their affinity the senator.

“I’m not 100 percent behind his platform but I like him as a person. For me it really comes down to authenticity,” says Edwards.We’ve seen so much deadlock in Congress and I think people are looking for someone who can be passionate and authentic rather than being partisan.”

Republicans who support Sanders don’t like being labeled liberals either, but that’s not enough to deter them: “There’s a mentality of ‘you’re either this or you’re that’, but the world doesn’t work that way,” DeFelice says. “Things aren’t always black or white. The world operates in shades of gray.”