by Paul Sonn, NELP Action

Labor Day has started the sprint to the November election. And with more than 40 percent of U.S. workers struggling on less than $15 an hour, our economy’s tilt toward low-paying jobs has become a top economic issue this year.

Now, as GOP leaders fret that Donald Trump may drag down Republican incumbents, turning more U.S. Senate races into toss-ups, the Republican majority’s stonewalling of any action to raise the federal minimum wage could cost the party control of Congress.

New polling shows that close to 70 percent of voters in key swing states want an increase in the federal minimum wage—and that 60 percent or more support a $15 minimum wage in six of the seven states polled.

Even more, the polling shows that candidates’ positions on raising pay could play a pivotal role in this year’s electoral battles for control of the U.S. Senate. The results show that the incumbent Republican U.S. senators locked in close races could lose critical support—and even their seats—over opposition to raising wages for working people.

In Pennsylvania, Wisconsin and New Hampshire, Democratic challengers Katie McGinty, Russ Feingold and Governor Maggie Hassan strengthened their leads over incumbent Republican Senators Pat Toomey, Ron Johnson and Kelly Ayotte when voters were made aware of the senators’ opposition to raising the minimum wage.

And in Arizona, Missouri and North Carolina, Democratic challengers Representative Ann Kirkpatrick, Jason Kander and Deborah Ross pulled ahead of Senators John McCain, Roy Blunt and Richard Burr, flipping those contests on their heads, when voters learned of the senators’ track records opposing raises.

For example, in Arizona—where John McCain has just emerged from his toughest re-election primary ever—a 43-43 tie turns into a 44-38 lead for Kirkpatrick once voters hear about McCain’s opposition to raising pay.

The polling comes as the National Employment Law Project Action Fund, the Center for Popular Democracy Action, the Working Families Organization and other grassroots groups in seven states begin to mobilize voters.

The coalition plans to engage in canvassing, hold candidate forums and wage debate protests, among other actions, to educate and energize voters around candidates’ positions on the raising the minimum wage.

While Donald Trump, who has been all over the map on the minimum wage, has announced he now supports an increase to $10, most Republicans in Congress remain opposed.

Leading Republican pollster Frank Luntz’s firm LuntzGlobal has warned minimum wage opponents, “If you’re fighting against the minimum wage increase, you’re fighting an uphill battle, because most Americans, even most Republicans, are OK with raising the minimum wage.”

While Congress has refused to act, over the past three and a half years, more than 50 states, cities and counties, as well as individual companies, have stepped forward to approve minimum wage increases, delivering raises to 17 million workers.

And 10 million of those workers are in states or cities that have approved phased-in $15 minimum wages, raising pay for more than one in three workers in California and New York and beginning to reverse decades of growing pay inequality.

Historically, raising the minimum wage enjoyed the same bipartisan backing in Congressthat it does with voters. But over the past 20 years, increasing polarization in Washington and the growing role of money in politics have led many Republicans to abandon their support.

As a result, the federal minimum wage today remains frozen at just $7.25 an hour. And taxpayers are being forced to pick up the tab, as low-wage workers in the seven states just polled must rely on $150 billion per year in public assistance to make up for their inadequate paychecks.

Candidates’ positions on the minimum wage have made a difference in close U.S. senate races before. Ten years ago, in Missouri and Montana, Democrats Claire McCaskill and Jon Testersuccessfully used their support for a higher minimum wage to highlight the difference between them and their opponents, Republican Senators Jim Talent and Conrad Burns, who both opposed raising the wage.

McCaskill and Tester rode the issue to an Election Day victory, helping to break a logjam in Congress and delivering the first federal minimum wage increase in 10 years in 2007.

With the public demanding action to boost pay, the Republican majority and individual candidates this fall face a clear choice: stop standing in the way of a long overdue federal minimum wage increase—or risk their political future.

Paul Sonn is general counsel and program director of the National Employment Law Project Action Fund.  This column was originally published at Newsweek.