In Iowa, Specter endorsement haunts Rick Santorum Reporting from Orange City, Iowa - As Rick Santorum rises in the polls, the Republican presidential candidate is receiving fresh scrutiny over his endorsement of moderate Republican incumbent Arlen Specter against a strong conservative challenger in the 2004 GOP Senate primary in his home state of Pennsylvania. At the first two stops of his final swing through western Iowa, the most conservative part of the state and his stronghold, Santorum was questioned about his endorsement of Specter, an abortion-rights supporter. The issue has simmered for months among Iowa activists, who use it to attack Santorum. It's been offered by Iowa insiders as a leading explanation for Santorum's failure to catch fire in the state earlier, despite the most extensive in-person campaign effort of any of the 2012 candidates. Now the issue is starting to get national attention as well. Rep. Ron Paul's son, Rand, a senator from Kentucky, raised it on a network talk show on Sunday. He mentioned it as an example of the problems Santorum has to overcome as he emerges as a top-tier contender in the caucuses. Polls show Santorum in a close race with Mitt Romney and Ron Paul for first place in Tuesday night's vote. "He was a big supporter of Arlen Specter against Pat Toomey," Rand Paul said on CBS. And a lot of people don't know that because he hasn't surged to the top yet so he hasn't had much scrutiny. When he has the scrutiny, I think he's going to have some of the same problems that some of the other fair-weather conservatives have had. Santorum describes the endorsement, which was in line with an effort by Bush White House adviser Karl Rove to back Specter in the '04 intraparty fight, as a "political decision." Santorum also acknowledges that it has hurt him and that even his wife, Karen, was opposed at the time. His explanation is fairly longwinded and complex -- rarely a plus in politics. As Santorum tells voters, Specter was then-chairman of the Senate Judiciary Committee, tasked with confirming Bush's nominees to the Supreme Court. At the time, the Republicans held a 51-49 seat majority and were in danger of losing their Senate majority. White House aides calculated that the veteran Specter had a much better chance of holding the Pennsylvania seat than Pat Toomey, the conservative challenger in the primary. Santorum praises Specter as a stalwart supporter of Republican judicial nominees, and uses the post-election confirmations of John Roberts in 2005 and Samuel Alito in 2006 to make his case. "I have no doubt that Sam Alito would not have been confirmed" without the re-elected Specter's help, Santorum maintains. "That's a pretty good trade, in my judgment," he adds. Specter won that 2004 primary by less than two percentage points over Pat Toomey, a prominent fiscal conservative. In 2009, a desperate Specter switched parties, becoming a Democrat in the face of a second primary challenge from Toomey. Specter ultimately lost in the Democratic primary to Rep. Joe Sestak, who then himself lost to Toomey in the tea party election of 2010. Santorum said he doesn't consider the Specter episode a blemish on his record, although he doesn't bring the issue up unless someone asks. He offers it as proof of his "willingness to take an arrow to do the right thing" - in this case, as he explains it to Iowa voters, putting additional conservative justices on the nation's highest court.