With the critical GOP presidential straw poll in Ames, Iowa, just three weeks in the offing, the rivalry between Minnesota Republicans Michele Bachmann and Tim Pawlenty is getting explosive. Pawlenty, in an interview from Iowa with CNN's Candy Crowley slated to run Sunday, is expected to use Bachmann as an example of why nobody has been elected president from the U.S. House in a century, repeating his increasingly common refrain that she has a "non-existent" record in Congress. Bachmann was asked about it Saturday after a campaign appearance in Marshalltown, Iowa. "What I have focused on is going against the agenda of growing big government in Washington," she said. "I have been very effective." Bachmann also dismissed reports that she has been incapacitated by chronic migraine attacks, an issue that has been giving Pawlenty headaches as well. "This week, they were talking about me and headaches," she told supporters in a packed conference room in the Marshalltown library. "All I want you to know is I've been giving a lot more headaches in Washington than I've been getting." The day before, at a pick-up hockey game in Des Moines, Pawlenty found himself answering reporters' questions about whether his camp was the source of the anonymous reports about Bachmann's headaches, which first appeared on the conservative Daily Caller Web site. One name that came up in the rink-side scrum with Pawlenty was ex-Bachmann chief of staff Ron Carey, a former Minnesota GOP Party chairman who has become a vocal Bachmann critic and Pawlenty supporter. Pawlenty said a check with his "senior staff" convinced him his people were not involved in the reports. Carey, who is not a Pawlenty staffer, did not return a call about the migraine reports this week. Meanwhile, Bachmann, like Pawlenty, has been trading on her love of guns and Second Amendment Rights. In response to an audience question in Marshalltown, Bachmann pointed out she was a big booster of the concealed-carry firearms law in Minnesota. Pawlenty, who spent part of Wednesday firing a 9 millimeter Glock semiautomatic pistol at a gun range in Madrid, bragged that he signed the concealed-carry bill twice as Minnesota governor. Not one to be upstaged, Bachmann told the citizens of Marshalltown, "I'm a permit holder myself."