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MUSCATINE, Iowa-On the banks of the Mississippi River here, Rick Santorum responded to the first on-air attack he's received from a candidate since he entered the race.

Santorum has been able to mostly fly under the radar and escape opponents' attacks, but since a poll yesterday showed him rising to third place after Mitt Romney and Ron Paul he is now no longer safe.

Rick Perry is out with a new radio ad hitting Santorum on earmarks and today on Fox News, Santorum responded.

"I said and I have after I left the Congress, I defended my earmarks in the sense that I'm proud of the money that I did set aside for things that were priorities in my state instead of having bureaucrats do that, but I recognize the American public sees this as a pox upon the Congress, " Santorum told Megyn Kelly. "As a president it's actually pretty easy for me to say I'll oppose congressional earmarks…. [W]ith Congress not earmarking that means as president I'll be able to allocate the resources accordingly. So it's not hard for Rick Perry or anybody running for president to be against congressional earmarks because it really just gives more power to the president."

The radio ad has a game show theme and links Santorum to earmarks he supported.

"Which Republican running for president voted for the Bridge to Nowhere earmark?" the ad asks before a "contestant" answers, "Rick Santorum."

"Correct!  Santorum voted for the Bridge to Nowhere and a highway bill full of pork." The ad also says Santorum "personally demanded more than one billion dollars of earmarks in his 16 years in Congress."

The ad ends with audio of Santorum himself saying he's "very proud of all the earmarks I've put in bills."

At his town hall this afternoon at the Button Factory restaurant here, he did not mention the Texas governor, but he again went after Ron Paul, attacking him for his foreign policy platform.

Calling himself "President Santorum," he said he believes open global shipping lanes lead to growth and development in the country, but that Paul would "take every ship that we have and bring it back and bring it back to port."

"He would abandon the seas to allow other countries to tell us what the rules are for transporting our goods. Let me assure you, they are not going to be as friendly as the U.S. Navy…. They are not going to be as cheap as the U.S. Navy is at securing those shipping lanes," Santorum told the crowd of about 100 people.

"Create Fortress Americana and leave the rest of the world to who? The Brits think they are going to step up? The French? How about the Belgians? The Dutch? The Chinese? The Russians?  How about the Iranians? I can go down the list."

For the second day in a row he compared the Texas Congressman to Dennis Kucinich and himself to Ronald Reagan.

"Iowa needs to send a message you don't want a candidate that is in the Dennis Kucinich wing of the Democratic Party running for president under our ticket," Santorum said. "You want a candidate that is in the Reagan wing of the Republican Party who believes in peace through strength.

He received a standing ovation from the packed room.  There was also a much larger media presence than usually trails the former Pennsylvania senator. MSNBC's Ed Schultz was in the crowd and at the very end of the town hall Santorum let him ask a question. Schultz asked about Mitt Romney's health care plan in Massachusetts and Romney calling it a "conservative principal" yesterday.

"I think it's a liberal principal to do something from the top down. The states have the right to do it; in my opinion the federal government does not. I would not as governor done that-I would have fought against that, provided an opportunity for people to get insurance instead, not mandating what insurance coverage they have," Santorum said.