The Bernie Sanders campaign released a new ad in Iowa this week, and it’s not like anything you’ll see from the GOP side. For one thing, it’s not an attack ad. Rather than talk about Hillary Clinton’s haircut or Martin O’Malley’s shoe size, Sanders sticks to the issues — and the issue, in this ad, is Big Oil.

The ad features two Iowa farmers, Patti Edwardson and George Naylor, discussing the Bakken pipeline, a proposed project that would move 570,000 barrels of crude oil through the state daily. The farmers, like Sanders, oppose the pipeline, which would be built at least partly on farmland seized through eminent domain.

“The fact that Bernie Sanders stands up against the pipeline is one of the reasons we support him,” says Edwardson. “Bernie Sanders has the guts to just stand up for what he believes in.”

“Bernie Sanders didn’t hesitate to say no to the big oil companies,” Naylor adds.

Clinton, in contrast, “has not voiced a firm position” on the Bakken pipeline, The Washington Post reports.

Sanders was a long-time, outspoken opponent of the Keystone XL pipeline, while Clinton came to her Keystone opposition late in the game. And while Sanders has pledged not to take donations from Big Oil, Clinton has some well-heeled friends in the dirty energy industry, and her wallet, it seems, is wide open.