Santorum, a former Pennsylvania U.S. senator, placed third in a CNN/Time/ORC poll of GOP Iowa caucus participants. He moved ahead of rival Newt Gingrich, but remains behind front-runner Mitt Romney and Ron Paul.
Santorum -- who was defeated in his bid for re-election to the Senate in 2006, losing by about 20 points to Democratic nominee Bob Casey -- said previous campaigns, in which he defeated incumbent Democrats, show he can win big races.
"I'm the only one in this race that has a track record of winning elections in tough states," Santorum told NBC's "Today" show, speaking from Coralville, Iowa. "I have to think that's one of the reasons that people in Iowa are looking at us and saying, 'Wow, this guy has defeated, straight up, two Democratic incumbents in very tough districts and in a very tough state.'"
Santorum said he believes he has the staying power his competitors lack.
"I've been through this grind before," he said. "I've run several tough statewide elections with national implications and have had the national media crawling all over my record for years and years and years.
"This has been different than everyone else that's sort of risen in this race, that they haven't been tested and we have. People know there's authenticity here, and they can trust me in what I say (is what) I'm going to do."