A proposal to build a mosque in Lower Manhattan just blocks away from the site of the Sept. 11 terrorist attacks has emerged as the hot-button issue of the moment in the midterm campaigns, putting candidates on the spot.

In Pennsylvania, the candidates for U.S. Senate are lining up on opposite sides of the question.

Republican Pat Toomey says he does not believe the mosque should be built there, while Rep. Joe Sestak, the Democratic nominee, says that guarantees of religious freedom in the Constitution confer the right for Muslims to worship anywhere - not that he's endorsing the specific project, mind you.

"It is provocative in the extreme to build a mosque in the shadow of ground zero," said Toomey spokeswoman Nachama Soloveichik. "Islamic leaders should be encouraged to move the mosque elsewhere."

Sestak's position echoes that of President Obama, who said Friday that allowing the mosque to be built is in keeping with the U.S. tradition of equal treatment of different faiths, but a day later the president recalibrated his remarks to say he was not speaking to the "wisdom" of building a mosque near ground zero.

"Joe believes there is a Constitutional right to religious freedom and separation of church and state that applies equally to all Americans," Sestak spokesman Jonathon Dworkin said. "But he is not looking to say what is best for New York – as long as that right is respected – he is focused on Pennsylvania."

On Tuesday morning, New York Mayor Mike Bloomberg, a Republican-turned-independent, is scheduled to campaign with Sestak in North Philadelphia. Bloomberg is a staunch supporter of the mosque project.