Florida Democrat Bill Nelson has changed his position on same-sex marriage, adding to a recent outbreak of support which has tipped the Senate in favour of marriage equality.

Mr Nelson told the Tampa Bay Times: “It is generally accepted in American law and U.S. society today ‘… that all Men are created equal, that they are endowed by their Creator with certain unalienable Rights, that among these are Life, Liberty and the Pursuit of Happiness.’ I believe that. The civil rights and responsibilities for one must pertain to all.

“Thus, to discriminate against one class and not another is wrong for me. If we are endowed by our Creator with rights, then why shouldn’t those be attainable by Gays and Lesbians?”

The statement seems to be a reversal of his stance, as last week Mr Nelson said that, while he has always supported civil unions, “My personal preference is that marriage is between a man and a woman.”

He now says he will add to “the petition of senators asking the Supreme Court to declare the law that prohibits gay marriage unconstitutional”.

The US Supreme Court Justices on 27 March 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 on 26 March the court heard arguments around Proposition 8, the state of California’s ban on equal marriage.

Only six of the 53 Democratic Senators have yet to come out in support for marriage equality, compared to 43 out of 45 Republicans.

Earlier this week Republican Senator Mark Kirk declared his support for equal marriage, saying: “Life comes down to who you love and who loves you back – government has no place in the middle.”

Republican Senator Rob Portman announced that he  endorsed same-sex marriage on 15 March.

The announcement was particularly surprising as Mr Portman had been one of the original sponsors of DOMA. He said the coming out of his gay son had prompted him to rethink his views.

Democratic Senator Timothy Kaine also shifted his position on Tuesday to support equal marriage.

He followed Democratic Senators Mark Begich and Mark Warner, who both came out in support of same-sex marriagebefore the Supreme Court’s hearings on the subject, following the precedent set by Claire McCaskill. Senator McCaskill announced her support via a Tumblr post.