Washington, DC (LifeNews.com) -- Sen. Bob Casey is one of just two Democrats in the Senate who take a pro-life position on abortion, but the Pennsylvania lawmaker has drawn significant criticism for endorsing Barack Obama. On Wednesday, the Catholic legislator defended the endorsement and claimed Obama isn't pro-abortion.

Obama has voted repeatedly in favor of taxpayer-funded abortions and opposes the partial-birth abortion ban and efforts to make sure parents are notified about their teenage daughters' abortions.

Casey is not only willing to overlook those votes that counter his pro-life views, but has gone as far as taping a television commercial backing his Illinois colleague.

"Some might characterize it that way, but I don't think it is" a pro-abortion vote or position, he told CNS News of his Obama endorsement. "I have a long (pro-life) record, and it's a lot harder for me. It's much easier to be a Republican and have that position."

"We have a definitive and certain disagreement on abortion," Casey told the conservative news web site. "I'm pro-life. (Obama) is pro-choice. I have supported legislation to outlaw partial-birth abortion. He doesn't agree with that."

CNS News asked Casey how supporting a pro-abortion presidential candidate squares with his Catholic faith and Casey responded that he backs Obama because of other political issues.

"I think it's possible in the next term of the president that they will directly or indirectly confront the issue of abortion, but they may not," Casey said. "But I'm certain that they will confront the issues - what are we going to do about the war, what about a $10 trillion debt, what about health care, the recession?

"You need to try to elect someone who you think can deal with a whole set of broad-based challenges," Casey added.

However, in a March 2006 letter to members of Congress, the U.S. Conference of Catholic Bishops made it clear that abortion is the number one political issues for Catholics.

"At the same time, we also need to reaffirm the Catholic Church's constant teaching that abortion is a grave violation of the most fundamental human right – the right to life that is inherent in all human beings, and that grounds every other right we possess," they wrote.

Some pro-life backers of Obama cite his desire to reduce abortions in other ways other than restricting them legislatively. But the Catholic bishops appear to believe that's not enough.

"While it is always necessary to work to reduce the number of abortions by providing alternatives and help to vulnerable parents and children, Catholic teaching calls all Catholics to work actively to restrain, restrict and bring to an end the destruction of unborn human life," the bishops wrote.

They said the Catholic members of Congress must remember "conscience must be consistent with fundamental moral principles."

"As members of the church, all Catholics are obliged to shape our consciences in accord with the moral teaching of the church," they added.

Wendy Wright, the president of Concerned Women for America, is one of the many pro-life groups and leaders who have contacted LifeNews.com with complaints about Casey's endorsement.

Pro-lifers have learned from painful past experience not to assume or expect that a candidate will be faithful to his – or his endorsers’ – religious affiliations," she told LifeNews.com. "Our litmus test is: Show us the beef. What is the candidate’s record?”

Meanwhile, William Donohue, president of the Catholic League, says Obama's killing a bill to provide medical care for babies who survive botched abortions shows how extreme the Democrat is on abortion.

"In 2003, while chairman of the Health and Human Services Committee of the Illinois Senate, he led the fight to oppose a bill that would have mandated health care for a baby who survived an abortion," Donohue explained.