Challenging the Republican ascendance in states where labor once carried enormous sway, a prominent union plans to spend tens of millions of dollars during the 2018 campaign cycle to reverse the trend.

The Service Employees International Union, one of the largest and wealthiest unions in the United States with roughly 2 million members, will fund an extensive campaign over the next 14 months to elect politicians with labor-friendly stands on the minimum wage, unions and health care.

The effort will primarily aim at the traditionally industrial states of the Midwest and Rust Belt, where labor’s political influence has come under a furious assault from conservative forces in recent decades, culminating in President Trump’s electoral sweep of the traditionally Democratic states of Michigan, Pennsylvania and Wisconsin.

Since 2010, four states in the region have enacted so-called right-to-work legislation that allows workers to opt out of paying fees to unions that bargain on their behalf. Elected leaders in several states have acted to block or reverse minimum-wage increases.