WASHINGTON - Sen. Bob Casey Jr. was told by opponents of abortion yesterday that they would be praying for him - and watching how he voted.

In a sometimes tense meeting, hundreds of Pennsylvanians on Capitol Hill for the annual March for Life rally questioned Casey about whether he was indebted to abortion-rights groups because of money he had taken in his 2006 campaign.

Even though Casey (D., Pa.) is opposed to abortion, there were widespread groans when he explained his support for the morning-after pill.

"We're going to continue to pray for you, and pray that you do what you know is right," Denise Johnston of Oakmont said.

Casey, speaking to a standing-room-only crowd in a Senate office building, answered questions for several minutes.

He said his opposition to abortion did not come from his Roman Catholic faith but because he believed, based on biology, that a fetus should be protected.

"I just don't think a church or a faith doctrine can dictate what you do as a public official," Casey said. "It can inform, I believe, and inspire, and be part of what you consider, but I think you have to make a determination as a public official based upon what you believe to be the truth."

He said he was not indebted to campaign contributors. "When they give me support, I don't say I'm going to carry your water on every issue," Casey said. "They know that we disagree."

He said he supported the morning-after pill because he believed it was contraception, and was one way to reduce the number of unwanted pregnancies. The pill is a high dose of the most common ingredient in regular birth-control pills that, taken within 72 hours of unprotected sex, can lower the chance of pregnancy by up to 89 percent.