Republicans are taking a page out of the Democratic playbook by seeking to make billionaire climate activist Tom Steyer into a midterm election bogeyman.

The latest effort comes in a new TV ad from the Republican super PAC American Crossroads attacking Rep. Bruce Braley (D) in the Iowa Senate race. The 30-second commercial hits Braley for voting against the Keystone XL pipeline after previously supporting it.

"Now, a California billionaire who stands to profit by blocking Keystone is spending big to help Braley's campaign," says the narrator as a picture of Steyer under the label "California billionaire Tom Steyer" appears on-screen.

The ad is reminiscent of a recent commercial Crossroads GPS, an affiliated nonprofit, ran in the Michigan Senate race. That commercial also sought to portray Steyer as a wealthy villain.

Democratic campaigns and groups have their own bogeymen: The Koch brothers. Democrats have routinely tried to link Republican candidates to the billionaire industrialist brothers who back conservative candidates and causes through groups like Americans for Prosperity.

Steyer's super PAC NextGen Climate Action Committee is running ads in some of the most competitive races in the country, including the Iowa and Michigan Senate races.

The challenge in trying to make Steyer and the Kochs into foils is that many voters don't know who they are. Polling has shown the Kochs are not very well known. It's hard to imagine Steyer is any more recognizable.

"Bruce Braley is focused on protecting and promoting Iowa's growing energy industry that brings billions of dollars into Iowa's economy each year, creates thousands of jobs, and reduces energy costs for Iowa families. So it's no surprise that State Sen. Ernst's out of state billionaire backers led by Karl Rove and big oil are attacking Braley," said Braley campaign spokesman Sam Lau in an e-mailed response to the new Crossroads ad, referencing Ernst, the Republican nominee.

Bobby Whithorne, a spokesman for NextGen Climate Action Committee, said in an e-mail, "The attacks coming from the Koch Brothers and their allies are rich, but not surprising."