When Tarie MacMillan switched on her television in August to watch the first Republican presidential debate, she expected to decide which candidate she would 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” who is challenging Hillary Clinton. MacMillan was a lifelong Republican voter until a few weeks ago when she switched her party affiliation to support the senator from Vermont in the primary. It will be the first time she’s 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 independent 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 such as 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 preordained 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.