A day after he announced that he had changed his stance to support equal marriage, US Senator Bob Casey has come under attack from a conservative group who accuse him of going “too far” in a quest to “redefine marriage”.

Amidst a rush of politicians to support equal marriage across the US, Democratic Senator Bob Casey yesterday announced his support for efforts to legalise it.

The Democratic Senator for Pennsylvania announced his support for equal marriage after previously supporting civil unions, and other pro-LGBT measures such as the repeal of Don’t Ask Don’t Tell.

In a press release, the American Family Association of Pennsylvania (AFA) said the Senator’s “evolution” on equal marriage was typical of many Democrats who now supported equal marriage.

The group said Casey, and other Democrats had “turned their backs on constituents and have leaped over the cliff and into the unknown territory or redefining society’s foundation 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 pressure is exerted by special interest groups that are seeking to redefine marriage and remake the United States.”

Gramley went on to criticise the Democratic Senator, who is Catholic, for what she said was rejecting his faith in favour of equal marriage, and the repeal of the Defense of Marriage Act.

The Democratic Senator had been criticised last week for being one of few Democrats in the Senate house who had not come out in support of equal marriage.

“Senator Bob Casey, Jr. does not have to face the voters for another six years and is willing to step over the same-sex ‘marriage’ cliff, in hopes that the voters will not remember his flip flop on this issue,” Gramley said. “Apparently, he hopes his decision to redefine marriage will not be an issue in 2018. I believe the exact opposite will be the case.”

She went on to say that the Senator, who was given endorsement by the Human Rights Campaign in 2006, now works with the group to introduce “homosexual special rights bills in the Senate”.

Casey was commended by LGBT rights advocacy groups Keystone Progress and Marriage Equality for Pennsylvania for his support for equal marriage.

“As a senator and as a citizen, I can no longer in good conscience take a position that denies her and her family the full measure of equality and respect,” Casey said on announcing his support.

Senator Casey defeated Republican Rick Santorum in the 2006 election, and was the first Democrat to be elected to a full term and win reelection in the US Senate from Pennsylvania since 1962.

The Supreme Court Justices on Wednesday indicated a possible interest in striking down the Defense of Marriage Act (DOMA), as it heard arguments around the issue.

This was the second day of hearings, as Tuesday the court heard arguments around Proposition 8, the state of California’s ban on equal marriage. Then the justices questioned the meaning of marriage, and challenged arguments for the ban. 

A decision by the Supreme Court in both cases is expected by the end of June.

Two Democratic Senators came out in support of same-sex marriage ahead of the Supreme Court’s hearings on the subject.

Missouri Democratic Senator Claire McCaskill already came out in support for marriage equality earlier on Monday, via a Tumblr post.

Aside from the Democrats to have come out as pro-equality, Republican Senator Rob Portman announced that he  endorsed same-sex marriage on 15 March.

The former US Secretary of State Hillary Clinton, officially announced her support for equal marriage in a moving speech last week in which she called moves towards equality “breathtaking and inspiring”.