New York Mayor Michael Bloomberg, the man without a political party, endorsed Democrat Joe Sestak for U.S. Senate on Tuesday as an independent thinker who he said would put Pennsylvania ahead of partisanship.

Trailing the mayor was the politically charged national debate over the proposed mosque and Islamic cultural center two blocks from the World Trade Center site, and sharp questions about the issue dominated their campaign event at the Sullivan Progress Plaza shopping center in North Philadelphia.

Bloomberg has strongly supported the mosque project. He says the nation cannot abandon its belief in religious freedom guaranteed by the Constitution.

Sestak, responding to questions, agreed.

"I strongly believe in the constitutional right of religious freedom and in the separation of church and state applying equally to everyone," said Sestak, a former Navy vice admiral serving his second term in the U.S. House. But, he added, "this is an issue for New York to resolve as long as it respects those constitutional rights. Let's stop playing politics with religion." The crowd of about 75 supporters applauded.

Sestak's Republican opponent, former Rep. Pat Toomey, says the Muslim group seeking to build the mosque and center should go elsewhere with the project out of sensitivity to the families of those killed at the trade center in the Sept. 11, 2001, attacks.

Robert Sklaroff, a physician and Republican activist from Elkins Park, questioned Sestak's judgment for speaking in 2007 to a Council on American-Islamic Relations dinner and said that the imam behind the mosque proposal had made anti-American statements on CBS's 60 Minutes.

"Look," Bloomberg said, "I would suggest you go from here directly to the library, get a copy of the Bill of Rights, and you'll realize that everybody has a right to say what they want to say. I happen to believe that that is the most important right that we have - the right to say what we want to say, which includes pray to whomever we want, in any place we want, in any manner we want."

Wendell Whitlock, chairman of the holding company for Sullivan Progress Plaza, denounced reporters for their mosque questions, calling the issue "contrived political crap" unrelated to the economy or other matters that affect people's lives.

Bloomberg, a lifelong Democrat who became a Republican and then turned independent in 2007, is serving his third term as mayor of the nation's largest city. He considered an independent presidential bid in 2008 and has endorsed a group of Republicans and Democrats this year who he says match his values, including Senate Majority Leader Harry Reid (D., Nev.) and Rep. Mark Kirk (R., Ill.), a candidate for Senate.

Sestak has displayed "leadership, independence, and results," Bloomberg said. He cited as an example of Sestak's independence his support for closing a loophole in federal law that allows sales at gun shows without background checks.

Toomey spokeswoman Nachama Soloveichik said the endorsement from Bloomberg, who she noted was a "Yankees fan," could not hide Sestak's record of voting in lockstep with the Democratic leadership, including House Speaker Nancy Pelosi.

Sestak and Bloomberg brushed off a disagreement on financial regulation, which Sestak has made a central part of his campaign.

Bloomberg, a billionaire former Wall Street trader who built the financial news and information company that bears his name, opposed aspects of the recently enacted law to tighten regulation of trading and banking - especially policies aimed at limiting the sale of credit-swap derivatives, the financial instruments blamed for the crash of 2008.

Sestak, on the other hand, has bashed derivatives trading and other Wall Street excesses, noting Toomey's former job as a trader and longtime advocacy of financial-industry deregulation.

"I don't agree or disagree 100 percent with anybody," Bloomberg said.

Sestak said his "critique is not on derivative trading at all," but on legislation in 1999 and 2000 that he said relaxed oversight of the trades "so there was no longer any transparency."

Later Tuesday, Bloomberg traveled to Washington to campaign for Democratic Mayor Adrian Fenty, who is in a tough reelection battle. Bloomberg also was hosting an evening fund-raiser in New York for Rep. Mike Castle (R., Del.), a moderate who is running for the U.S. Senate.

When the Progress Plaza event ended, Bloomberg and Sestak went into the Fresh Grocer store to order cheesesteaks to go.

Bloomberg asked for hot sauce on his sandwich, but he said he was determined not to order Swiss cheese, showing he was savvy enough about local customs to avoid 2004 presidential candidate John Kerry's faux pas.

"You'll have to ask the man behind the counter," Bloomberg said when asked about the cheese. "I told him to pick it." (It was American cheese, the counterman said.)