Santorum's new ad–now running statewide–criticizes his Democratic challenger, Bob Casey Jr., the state treasurer, for saying he would vote yes for the immigration bill passed by the Senate this year that would provide a path to citizenship for illegal immigrants. Santorum voted against the bill, which is now stalled in Congress because House Republicans oppose it, arguing that the bill amounts to "amnesty" for immigrants who broke the law.

"Bob Casey's support of this legislation is a slap in the face to hardworking Americans," says Vince Galko, Santorum's campaign manager. "Pennsylvanians deserve to know the vast difference between Rick Santorum, who voted no on giving illegal immigrants amnesty, and Bob Casey Jr., who believes those who broke the law should get a better deal than those who came to this country by following the law."

The Santorum campaign ran a similar television ad on immigration several months ago. In addition to the ad, the Santorum campaign held a town meeting on immigration at Grove City College in Mercer County on Friday. The campaign also launched a new website, www.caseyforamnesty.com, and is distributing new "Casey for Amnesty" yard signs and bumper stickers.

Casey has said that he would support the Senate immigration bill but added that the "bill is not perfect it is a consensus bill it is long past time to take action, and this bill contains important reforms."

Larry Smar, Casey's spokesman, says the ad hides the fact that Santorum and other Republicans failed to reach consensus and do something about immigration. "If Rick Santorum spent this much time and energy working on illegal immigration in the Senate, we may have gotten more than a fence," says Smar, referring to a bill recently passed by Congress that would provide partial funding for 700 miles of metal fencing along the U.S.-Mexico border.

Smar pointed out that even Sen. Arlen Specter–a Pennsylvania Republican who supports Santorum–supports the Senate immigration plan. "If there's not legislation with Republicans in charge there's going to be blame here, and justifiable blame, if we do not produce a bill," Specter told the New York Times last month.

The Casey campaign is running its own ad on immigration that criticizes Santorum for voting against funding for more border patrol agents. The Santorum campaign argues that Santorum did not vote for these measures because they would have increased the deficit and did not increase the government's capacity to train more patrol agents.

—Danielle Knight