For Republicans this year, the minimum wage is the wedge issue from hell.

Even as Democrats lurch toward a potentially disastrous midterm election, support for raising the federal minimum wage is resonating with voters. In fact, it may be the only issue on which Democrats are winning: A Pew Research Center poll earlier this year found 90 percent of Democrats and 53 percent of Republicans favored raising the federal minimum to $10.10 from its current $7.25, as proposed by President Barack Obama.

Four Republican-leaning states have state-level minimum wage increases on the ballot this year — Alaska ($9.75), Arkansas ($8.50), Nebraska ($9), and South Dakota ($8.50) — and the increases will likely pass in all four. The same goes for a non-binding Illinois referendum on raising the minimum wage to $10. Democrats anticipate these measures will boost Democratic turnout in all five states, particularly among African-Americans.

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“It gives Democrats a concrete offer on what is increasingly seen as the main problem,” says Democratic pollster Stan Greenberg. “Jobs that don’t pay enough to live on … people know what a struggle it is for low-wage workers.”

Republicans remain confident they’ll retake the Senate, but that’s partly because some have defused the issue by endorsing the ballot measures. As recently as January, Alaska Republican challenger Dan Sullivan said, “Raising the minimum wage isn’t an answer” even as his Democratic opponent, Sen. Mark Begich, backed Obama’s proposed federal increase to $10.10. By September, though, Sullivan was telling The Wall Street Journal he would vote for the Alaska increase “because it is a state-driven initiative.” Afterwards, Sullivan, who’d trailed Begich much of the summer, widened his lead by two or three points.

Similarly, in Arkansas, the Republican Senate challenger, Rep. Tom Cotton, was silent on that state’s proposed hike for much of the year before declaring in September that, like his Democratic opponent, Sen. Mark Pryor, he would vote for the Arkansas pay hike. Republican former Rep. Asa Hutchinson, who’s running for Arkansas governor, did the same. In the House, Cotton voted against hiking the federal minimum. Hutchinson previously opposed the ballot measure.

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Pryor, the rare Democrat who opposes the federal increase, skipped the April Senate vote for a tour of Arkansas tornado damage with the president. Cotton took the lead soon after, and widened it after he endorsed the higher state minimum. Hutchinson consistently polls ahead of his Democratic opponent, former Democratic Rep. Mike Ross.

GOP candidates can’t always make the issue go away by switching sides. Illinois gubernatorial candidate Bruce Rauner, the former chairman of a private-equity firm, started out favoring either eliminating the state’s minimum wage or reducing it from $8.25 to $7.25 (which is what the federal minimum is). Later Rauner said he preferred raising the national minimum (because raising the state minimum might give an advantage to neighboring states with lower minimums) but that he would support raising the state minimum if certain conditions were met.

For neither the federal nor the state minimum did Rauner specify how high he’d raise it. That left Rauner’s Democratic opponent, Gov. Pat Quinn, an opening to attack. Quinn, who spent a week last summer attempting to live on the minimum wage, has built much of his campaign around the issue. Polls show the race is very close.

Even in states that don’t have minimum wage on the ballot, opposition to an increase may put some Republicans at risk. “I think it’s playing quite successfully as a wedge issue,” says Arun Ivatury, campaign strategist for the National Employment Law Project Action Fund.

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Ivatury thinks the issue may weigh heavily in Wisconsin, where Republican governor Scott Walker is in a dead heat against Democrat Mary Burke, a former state commerce secretary. Walker caught heat for telling the Milwaukee Journal Sentinel that he didn’t think the minimum wage “serves a purpose” and for certifying, through the state’s Department of Workforce Development, that Wisconsin’s current $7.25 minimum constitutes a “living wage.” AFL-CIO President Richard Trumka said recently on MSNBC that “It’s not been tough for us to get volunteers in Wisconsin, because this guy is known as an anti-worker governor.”

In the Iowa and North Carolina Senate races, Ivatury notes, Republican candidates are getting attacked for questioning the necessity of a federal minimum wage — and both races remain fairly close.

Iowa state Sen. Joni Ernst has recently denied ever saying she opposed a federal minimum (the public record contradicts her), and now says only that she doesn’t want to raise it. In her race to fill retiring Sen. Tom Harkin’s seat, she’s running slightly ahead of Democratic Rep. Bruce Braley, who supports the federal increase to $10.10.