US Senator Timothy Kaine said on Tuesday that “labels are important” when considering the debate around equal marriage, and announced that he had shifted his position to fully support equal marriage.

The Democratic Senator had previously been supportive of offering equal rights to gay and lesbian couples, but had been reluctant to accept the term “marriage”, to refer to same-sex relationships. He has now said he supports marriage equality, and that term to describe it.

“I think any couple should get the same legal rights that my wife and I get,” Kaine said. “I think that’s the issue that’s before the Supreme Court, is whether people should be treated equally legally, and I think they should. I’m very comfortable with marriage. Some would describe that relationship and use a different label. Labels are important, but the key is . . . it’s got to come with all the same rights.”

On Tuesday an aide to Kaine said: “Senator Kaine supports same-sex marriage. When recently asked to weigh in on the Supreme Court cases, he made clear that he hoped the court affirmed the right of all couples to get married and enjoy the same right and responsibilities as he and Anne.”

Until 2012, when US Vice President Joe Biden said he was “absolutely comfortable” with equal marriage, Kaine had maintained that he was uncomfortable with accepting the term for same-sex relationships.

At an event in May 2012, Kaine said: “I believe in the legal equality of relationships… The debate about, you know, is it marriage? Is it civil union? Is it domestic partnership? I just kind of let that one go and say should committed couples be treated the same by law, and I think the answer is yes.”

But when he was asked by reporters whether marriage was a civil rights issue, Kaine responded that “relationship equality is a civil right,” and when he was asked about “marriage licenses” for same-sex couples, Kaine responded that “the labels get in the way of the issue.”

Earlier this year, Kaine joined over 200 members of Congress who signed an amicus brieft to the Supreme Court urging it to strike down the Defense of Marriage Act as unconstitutional.

In 2006 as a governor, he campaigned against a Virginia constitutional amendment to ban equal marriage, despite then saying he personally thought marriage was between one man and one woman.

The amendment passed 57% for and 43% against, but a Washington Post poll last year showed that 49% of people supported equal marriage compared to 40% against.

This does not line up with a new poll this week, which revealed that, despite rising support for equal marriage overall across the US, voters in the state of Virginia still marginally oppose it.

Two Democratic Senators, Mark Begich and Mark Warner both came out in support of same-sex marriage last week before the Supreme Court’s hearings on the subject, following the precedent set by Claire McCaskill.

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 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.