<text>  Des Moines, Iowa CNNFor Iowas economy, corn is everything. So its no surprise that the Republican governor and other powerful voices in state agribusiness are vocal backers of the Renewable Fuel Standard, a federal rule that requires gasoline to be comprised of up to 10 in renewable fuels. One of those is ethanol -- with corn often a key ingredient. Dont mess with the RFS, Gov. Terry Branstad said Saturday, offering a not so subtle warning as he kicked off a daylong agriculture summit that featured a string of likely Republican presidential candidates. The RFS is a major issue that White House hopefuls are forced to address whenever they visit the No. 1 corn-producing state that also goes first in the presidential nominating calendar. But its a less popular policy for small government conservatives, who decry the mandate as federal overreach in the private sector. In his first 2016 visit to Iowa, Jeb Bush sought to delicately explain his desire to see the RFS disappear over time. The markets ultimately going to have to decide this, he told the audience at the event, which took place at the Iowa State Fairgrounds. Bush acknowledged that the mandate, which passed in 2007, has helped lower dependence on foreign oil and boost corn-heavy economies. But as we move forward over the long haul, there should be certainty for people to invest, he argued, saying ethanol will no longer need help from the government. So at some point well see a reduction of the RFS need, because ethanol will be such a valuable part of the energy feedstock for our country. He declined, however, to suggest when exactly that may happen. In his remarks, Bush also defended his position in favor of legal status for undocumented immigrants after they meet a wide set of requirements. And while attending a fundraiser Friday night in Des Moines, he stood by his support for Common Core, the controversial testing standards that have become a point of contention for conservatives. Election 2016: Jeb Bush makes his first Iowa foray . Bushs frank statements on the RFS and his defense of some of his most controversial views indicated that the former Florida governor plans on sticking with his positions as he gets ready to hit the campaign trail, no matter how unpopular they may be to certain audiences. Still, he was not totally immune to at least some pandering. Bush told the crowd that hell be cooking some Iowa beef Sunday when hes back home with his family in Florida, adding that hell probably make some really good guacamole, too. Talking about campaigning for his fathers presidential campaigns in Iowa, Bush said he went to at least 50 counties. I remember eating really well -- eating really, really well. With a John Deere tractor towering near the stage, each candidate sat on stage for a 20-minute QA with Bruce Rastetter, an agribusiness entrepreneur and major Republican donor in Iowa. The audience of close to 1,200 was comprised largely of farmers and other leaders in the agriculture industry. While Bush took a mild approach to the RFS, Sen. Ted Cruz of Texas flat out opposed it, saying Washington shouldnt be picking winners and losers. I have every bit of faith that businesses can continue to compete and continue to do well without having to go on bended knee asking for subsidies, asking for special favors, he said. I think thats how we got in this problem to begin win. Ethanol proponents argue that because oil companies own gas stations, consumers are unable to access ethanol and therefore it needs the governments support to break through oils stronghold of the market. Cruz acknowledged that his view wouldnt be well-received, but tried to argue that it proved his authenticity. Look, I recognize that this is a gathering of a lot of folks who the answer youd like me to give is, Im for the RFS, darn it. Thatd be the easy thing to do. But Ill tell ya, people are pretty fed up, I think, with politicians that run around and tell one group one thing, tell another group another thing. Former Texas Gov. Rick Perry took a similar stance and defended his decision to request a waiver that would exempt Texas from the federal mandate. If individual states want to require that ethanol be used in gasoline, thats fine, he said, but not the federal government. I philosophically dont agree that Washington, D.C. needs to be making these decision that affect ... our agriculture industry, Perry said. Other contenders offered entirely opposite positions. New Jersey Gov. Chris Christie, for example, said he absolutely supports the RFS. Thats what the law requires. So lets make sure we comply with the law. That should be the minimum, he said, drawing applause from the crowd. Rick Santorum, who won the Iowa caucuses in 2012, ticked off what he called a laundry list of benefits, including more energy independence and more jobs for farmers. It is very important for rural Americans, said the former senator from Pennsylvania. For his part, Mike Huckabee argued that the ethanol mandate was a matter of national security. America needs to do three things to be free: feed itself, fuel itself, fight for itself, the former Arkansas governor said, adding that relying on foreign governments for energy leads to a weakened United States. Huckabee, who won the Iowa caucuses in 2008, hit back at criticism that politicians like him simply support the RFS for political reasons. The decisions are made not just frankly for whats best for Iowa -- thats not the rationale. You cant make a decision and say, Its good for Iowa. Gee, theyre the caucus state, we better suck up to them. We better make decisions that are good for every consumer, he said. Wisconsin Gov. Scott Walker, whos had a strong showing in polls since he visited the state in January, made clear that while hes generally a free market guy, he believes ethanol is being blocked from consumers and needs government assistance. Right now, we dont have a free and open marketplace, and so thats why Im willing to take that position, he said. But, similar to Bush, Walker said that he expects ethanol can one day compete openly and you no longer need in the industry to have these subsidies. The audience at Saturdays event was largely subdued, given the tone and dialogue of the summit was more substance, less red meat. Those who supported the RFS, however, received a strong response from the crowd. As for those who opposed it, Bill Couser, who co-chairs a campaign called Americas Renewable Future which pushes the ethanol mandate, said hes not ready to write anyone off quite yet. But those candidates can expect to hear a lot more from him in the coming months. Maybe I didnt like a few of their answers, but its going to give me some time to go help them understand the issues, he said. 