North Carolina's Kay Hagan on Wednesday became the sixth Democratic senator to endorse gay marriage this week as the Supreme Court hears two cases on the issue.
"After much thought and prayer, I have come to my own personal conclusion that we shouldn't tell people who they can love or who they can marry," Hagan said in a statement on her Facebook page on Wednesday.
Although public opinion polls show a majority of Americans believe that homosexuals should have the right to wed, support varies between states.
Hagan is up for re-election next year in a state that backed Republican Mitt Romney—an opponent of gay marriage—in the November 2012 presidential election, and where voters also strongly backed a measure in May 2012 prohibiting both civil unions and domestic partnerships.
Five other Senate Democrats—Mark Begich of Alaska, Claire McCaskill of Missouri, Jay Rockefeller of West Virginia, Jon Tester of Montana and Mark Warner of Virginia—have also announced their support for gay marriage in the last few days.
Their backing left only about 10 of the 55 members of the Senate Democratic caucus who have not endorsed same-sex marriage, reflecting a shift in public sentiment.
Hagan's announcement came as the Supreme Court heard arguments on Tuesday and Wednesday on two gay marriage cases. The justices on Wednesday indicated interest in striking down a 1996 law that denies federal benefits to legally married same-sex couples.
President Barack Obama announced that he approved of gay marriage in May 2012.
Republicans, who are generally more socially conservative than Democrats, remain largely opposed.
Ohio Sen. Rob Portman became one of the most prominent Republican politicians to back gay rights in mid-March when he announced his support for same-sex marriage, two years after his son told him he was gay.
Hagan compared her decision to Portman's in her statement on Wednesday.
Reporting by Patricia Zengerle; Editing by Eric Beech
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