Cruz kicked off his six-day bus tour across Iowa and received questions at his first event about his opposition to the the Renewable Fuel Standard (RFS), an ethanol subsidy that many Iowan farmers depend on.
"I very strongly support corn and farmers and ethanol, but I don't think Washington should pick winners and losers" Cruz said after a supporter asked him to clarify his stance.
"I think what we need to do, instead of having a government mandated subsidy, we ought to do is remove the government barriers so that ethanol can end up having a larger share of the market through competition rather than through government putting mandates in place," Cruz added.
According to a report from Politico, supporters of the Renewable Fuel Standard are buying newspaper, radio and digital ads to attack Cruz on the issue in Iowa. Another group, Iowa Progress Project, has spent $200,000 airing anti-Cruz ads.
Cruz has overtaken Trump in the polls in Iowa, with 40 percent of likely Republican Iowa Caucus voters saying they plan on voting for Cruz.