A democrat running a long-shot bid to unseat a Republican incumbent in Arizona has released one of the most searing adverts of the 2018 midterm season, with some pretty damning testimonial from some very surprising voters.

The advert features several people attacking Representative Paul Gosar on a range of issues from health care to immigration to the environment. Mr Gosar, they say, is unfit for office.

Here’s the catch: The naysayers are Mr Gosar’s siblings.

The advert spread online Friday evening, with what appeared to be pretty run-of-the-mill voter testimonial for an attack advert. Then Tim, David, Grace, Joan, Gaston, and Jennifer Gosar revealed themselves as the congressman’s family.

“If he actually cared about people in rural Arizona, I bet he'd be fighting for Social Security, for better access to health care,” Jennifer Gosar said. “I bet he would be researching what is the most insightful water policy to help the environment of Arizona sustain itself and be successful.”

“He's not listening to you, and he doesn't have your interests at heart,” said Tim Gosar, who made the final plea to Arizona voters to elect democrat David Brill.

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The advert is not the first time that Mr Gosar’s family has publicly rebuked the Republican, who represents a district that stretches from northeastern Arizona down alongside the border until hitting part of Yuma, in the far south of the state. The district is massive, and encompasses largely rural parts of the state.

Last October, brother David Gosar told The Phoenix New Times that he and his family have been anything but shy in their attempt to warn Arizonans about the policies their brother supports – and that they, clearly, do not appreciate.

“There's no dispute about our opposition to him,” David Gosar told the newspaper. “It's something that has been building for some time. Watching what he does up there in Congress. It's ridiculous.”