It isn't often that indie musicians throw benefit concerts for presidential campaigns. But the dark-horse efforts of Vermont's socialist senator, Bernie Sanders, aren't the usual gambit for the White House.

In addition to forgoing the traditional donor base, Sanders is largely relying on small donations from supporters and the support of the occasional left-wing union. Many of his small donors are millennials, as the 74-year-old candidate has proven particularly appealing to young people. The younger the age cohort, polls have repeatedly shown, the more popular he gets.

Don't expect a fund-raiser for Hillary Clinton at South Philly's 150-capacity Boot & Saddle. Not that such an event would be unwelcome, but a $1,500 haul - the maximum take for the Sanders benefit - probably wouldn't be of much interest to the front-runner's campaign.

Instead, on Wednesday, Philadelphia will have the opportunity to rock out for socialism, of the Nordic variety. The organizers have coordinated with staffers to a limited extent, and all the proceeds, after expenses, will go to Sanders' campaign. The price of drinks and food will not be socialized.

Similar shows in support of Sanders have cropped up in Brooklyn, Boston, Chicago, and Portland, Ore. But this is the first Sanders concert in Philadelphia, and its organizers are not political operatives by any stretch of the imagination.

"I spend time mostly in arts or music scenes, and most of my friends are not politically active," says Jon Coyle, organizer of the fund-raiser and the vocalist and keyboardist for the experimental pop band Son Step. "I've never been part of a politically committed event either, so this is quite new to me. But I've been following his campaign since day one, and he's such a loved guy among my artistic friends that I figured this would be a good way to win support for him."

The Philly for Bernie Sanders concert features Son Step and two other idiosyncratic Philly pop bands, Laser Background and On The Water. The show is 7 to 11 p.m. Wednesday at Boot & Saddle, 1131 S Broad St., a 21-and-over venue. Admission is $10.

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