Pennsylvania Senator Bob Casey, Jr., a Democrat, is under attack for endorsing gay marriage.

Casey, a Catholic, announced his new stance on the issue on Monday.

“As a senator and as a citizen, I can no longer in good conscience take a position that denies [gay couples] the full measure of equality and respect,” he said in a statement given to the Philadelphia Gay News.

The Christian conservative American Family Association assailed Casey, a long supporter of civil unions, saying that he had “leaped over the cliff and into the unknown territory of redefining society's foundational block.”

“Casey's support of civil unions which have been used as a stepping stone to same-sex marriage in every state they've been legalized was troubling enough, but for him to totally reject one man one woman marriage as God's only plan for marriage is a bridge too far,” said Diane Gramley, president of AFA. “We need strong leaders who are willing to stand up and do what is right no matter what type of pressure is exerted by special interest groups that are seeking to redefine marriage and remake the United States.”

Scranton Bishop Joseph C. Bambera said that “Casey's position is contrary to the teaching of the Catholic Church.”

“Senator Casey has unfortunately and disappointingly set aside the Catholic belief and teaching that the sacrament of marriage, rooted in the natural law, is a faithful, exclusive, lifelong, loving union of a man and a woman open to the transmission of human life,” Bambera said in a statement.

With the Tuesday announcement that Illinois Senator Mark Kirk, a Republican, favors marriage equality, the Senate is now evenly divided on the issue.