Terry Hayes is fed up. Like a lot of people, she’s become disillusioned with both the Democratic and Republican parties and is ready for something new. “It’s not just the parties that are the problem -- partisanship is the problem,” she says. “There’s an expectation that there’s just one right way.”

That’s why Hayes, the state treasurer of Maine, is running for governor as an independent. The former Democrat is hoping to become the third independent to be elected governor of Maine in the past half-century. She says that if she ran as a Democrat, she’d be expected to hew the party line on all issues. She’s not willing to do that.

And she’s not alone. Several other candidates in Maine are running as independents or under third-party banners. In Alaska, Bill Walker, currently the nation’s only independent governor, is seeking reelection. And experienced or well-funded independent candidates are running for governor or exploring bids in Arizona, Connecticut, Kansas, Nebraska and Rhode Island. “There have always been independent candidates,” says Joel Searby, senior strategist for the Centrist Project, which supports independents. “The difference is the caliber of candidates and the organization and infrastructure behind them.”

With both parties seeming to move to their respective ideological extremes -- Republicans to the right and Democrats to the left -- it seems like there should be plenty of room in the middle for centrist candidates, says Marjorie Hershey, an expert on political parties at Indiana University. The problem, she says, is that while voters may feel disaffected with the two parties, they aren’t all upset for the same reasons. Typically, self-described independents, who tend to lean toward one party or the other, will shy away from a party’s platform on some issues but embrace it on others. “The people in the middle aren’t necessarily moderate,” Hershey says. “They’re just inconsistently extremist -- right-wing on some things and left on others.”

As an example, former Republican state Rep. Joe Trillo is running for governor as an independent in Rhode Island not as a moderate, but because he feels the state GOP has been insufficiently supportive of President Trump.

According to Gallup, the number of self-identified independent voters has ticked down over the past year, with more people choosing sides in the Trump era. Independent candidates have always had a tough road ahead of them. The two main parties enjoy huge structural advantages. But independents can win, especially when they start out with high profiles, lots of resources and face a field where support is fractured for some reason.

“You can’t say independents are the wave of the future,” says Darryl Paulson, a political scientist at the University of South Florida, “but you probably can say that the door has been opened to independent candidates far more than before, and we’re going to see more of them.”