Just as Republican presidential candidate Ted Cruz is surging in the Iowa polls, his failure to kowtow to the powerful ethanol lobby there has produced an onslaught of special interest attack ads.

The pro-ethanol group America’s Renewable Future (ARF) recently started running radio ads in Iowa targeting Cruz over his opposition to the Renewable Fuel Standard (RFS), a federal mandate that is a boon for the ethanol industry.

“Cruz backs policies that threaten rural Iowa and thousands of jobs,” warn the radio spots, which according to Majda Sarkic, a spokesperson at the organization, will be buttressed with mailers and digital advertising. The first-in-the-nation Iowa caucuses are on February 1.

The ads come on top of a nearly yearlong campaign by the organization to pressure candidates in both presidential primaries to support the Renewable Fuel Standard and ethanol. ARF was registered in Iowa in December 2014 by Eric Branstad, son of Iowa’s Republican governor, Terry Branstad, and a partner at the public relations firm Matchpoint Strategies. The venture was bipartisan: Branstad co-founded the organization with Iowa Democratic Party alum Derek Eadon of the political firm Blueprint Strategies.

Sarkic, the spokesperson, previously worked for Democratic lawmakers and campaigns, including Organizing for America. Although the organization is not required to disclose its funding, organizers told the Des Moines Register that they were being financed by the Iowa Corn Growers Association, the Iowa Renewable Fuels Association, and Growth Energy, all of which represent industry that benefits from the RFS.

For the past few months, ethanol advocates have peppered Republican candidates with questions at town halls. ARF’s YouTube page features exchanges involving Jeb Bush, Rand Paul, John Kasich, Marco Rubio, Donald Trump, Scott Walker, Martin O’Malley, Bobby Jindal, Ben Carson, Rick Perry, Mike Huckabee, Rick Santorum, and Cruz.

The majority of candidates in these videos affirmed their support for the renewable standard, or proposed expanding it further. ARF used these answers to help put together an online scoreboard where three candidates — Cruz, Carson, and Paul – received failing grades.

Branstad told reporters in Des Moines that ARF chose to target Cruz because he alone has refused to meet with them. “Of all the letters, emails and invites, he’s the only one that has not given us the time to sit down with us and talk to us about what this means to Iowa.” All the others have either met with them or toured a biofuel plant.

Cruz has been surging in Iowa, challenging Trump, who the group praised for saying he is “totally in favor of ethanol. I will support it 100 percent.”

ARF has used a number of other advocacy tools to push its pro-ethanol agenda in Iowa, including Change.org petitions, outreach with mechanical bulls, and cutting an ad with Chris Soules, who is both an Iowa farmer and a reality TV star featured on The Bachelor.