Image Credit: Scott Olson/Getty Images

SIOUX CENTER, Iowa - Fliers criticizing Rick Santorum were scattered throughout his event Monday at a small Christian college here in the Northwest part of the state, forcing the GOP presidential candidate to explain to the  audience why he supported a moderate Republican during their time together in the U.S. Senate.

The white paper reads, "Why Rick Santorum is not fit to serve as President of the United States" and criticizes Santorum for endorsing Arlen Specter over the more conservative and now senator from Pennsylvania, Pat Toomey.

"It is well established that Rick Santorum aggressively campaigned for now-Democrat U.S. Senator Arlen Specter, one of the most pro-abortion Senators serving in the U.S. Senate - over a strongly pro-life primary opponent," the flier reads.

Santorum is anti-abortion rights and talks about it on the stump almost every day, but his endorsement of Specter has found its way on to anti-Santorum literature at events across the Hawkeye State.

He addressed the fliers at Monday's event, telling the crowd he supported Specter because he was the chairman of the Senate's Judiciary Committee and promised Santorum that he would help usher in President Bush's Supreme Court nominees.

After the event at Dordt College, where Santorum supporters numbered more than 100, the former Pennsylvania senator told reporters the literature doesn't bother him and "it's part of the campaign."

"At least I don't have a bunch of steel workers trying to storm the podium. I used to campaign in some pretty rough areas in Pennsylvania so this is very calm by comparison," Santorum said of the private, Christian liberal arts college. "I want the tough questions, if people have concerns about me I want to hear those concerns."

Santorum, 53, told the crowd at the student campus center that even if they aren't going to support him, to go help one of his opponents.

"This is the most important election of your life. I personally believe if you sign this form, sign up and help us. But if you want to say, 'No, he's not the guy I'm for,' then go sign up and help somebody else. Do not set on the sidelines," Santorum said.

At an earlier event in the rural town of Sanborn, he expressed some veiled attacks at his opponents, telling Iowans at Jay's restaurant that despite being down in the polls, he can still win the caucuses here in a month.

"I wasn't for the Wall Street bailouts and now against them. I wasn't for cap and trade and believing in man-made global warming and now I'm against it," Santorum said. "I wasn't for single pay, I mean individual mandates and health care, top-down government health care and now I'm against it."

Santorum confirmed Monday that he would participate in the Newsmax ION Television debate this month moderated by Donald Trump. He said as soon as Newt Gingrich signed up, he was in.

"I think we make too much of the questioner and as if that, I don't think they're going to make that much of a difference in this debate or any other debate," Santorum said, referring to Trump.

Despite barnstorming the state and visiting all 99 counties of Iowa, Santorum is still struggling in the polls, only reaching 6 percent support of likely caucus-goers in the Des Moines Register poll released this weekend.