But a former Kennedy staffer challenged that interpretation, telling the Massachusetts newspaper The Republican that the bill did not mandate any benefits and was not meant to endorse such exemptions.

Brown has also cited 1995 legislation sponsored by Kennedy which included a provision preventing a doctor or hospital from being forced to perform a procedure in violation of their personal beliefs.

The senator said his evidence includes a letter from Kennedy to the pope.

In a 2009 letter to Pope Benedict XVI, Sen. Kennedy said, "I believe in a conscience protection for Catholics in the health care field and will continue to advocate for it as my colleagues in the Senate and I work to develop an overall national health policy that guarantees health care for everyone."

Sen. Kennedy's son, former U.S. Rep. Patrick Kennedy, also asked that the ad be pulled. He said that his father agreed that health care providers like doctors and hospitals should be allowed a conscience exemption for performing any service. But his father would have opposed the Blunt amendment, he said.

The Respect for Rights of Conscience Act, also known as the Blunt amendment, was tabled by the U.S. Senate in a 51-48 vote March 1. The amendment, attached to a key highway bill, would guarantee the protection of conscience rights in all aspects of implementation of the health care reform law. Brown voted in favor of the amendment while Sen. John Kerry, voted against it.

According to the Associated Press, Brown said Feb. 27 he would not be pressured into pulling the ad.

The Republican's chief Democratic rival, Harvard Law School professor Elizabeth Warren, also called for Brown to take down the ad.

Warren said the amendment would have created a hole in health care coverage and could result in women being denied "preventive health care" for any reason.

Brown said Warren's concerns are "red herrings."

The Brown campaign ad was finally replaced March 2 with a new ad on Brown's support of allowing women to serve in combat roles. Brown's spokesman told the Boston Globe that the previous ad ''ran for a week, which is the usual cycle for the Scott Brown radio reports.''