Bernie Sanders wants his backers to back Russ Feingold with votes in this fall’s U.S. Senate race in Wisconsin — and with the sort of small campaign contributions that have powered the Vermont senator’s 2016 presidential bid. Making his first such appeal in a Senate race, Sanders emailed his national fundraising list with a message of support for Feingold’s Democratic challenge to Wisconsin Sen. Ron Johnson, a right-wing Republican who has talked of campaigning with Donald Trump as “the Ronald and the Donald.”

“We are going to have to elect candidates up and down the ballot who recognize that it is too late for establishment politics and economics,” Sanders wrote. “Candidates like my friend, former U.S. Sen. Russ Feingold.”

Feingold leads in Wisconsin polls. But everyone knows money will flow to Johnson from the corporate interests and billionaires that appreciate his steady service to their interests. But Sanders has a model for countering big money with small money.