While appearing on MSNBC's "Morning Joe," Duncan was asked by Mark Halperin, "Do you believe that same sex men and women should be able to get legally married in the United States?"
Duncan responded, "Yes, I do," according to Politico.
Halperin followed up his answer asking, "Have you ever said that publicly before?" and Duncan replied, "I don’t think I’ve ever been asked publicly," according to MSNBC.
Duncan's support came just a day after Vice President Joe Biden very candidly expressed his own views on the topic, telling NBC's "Meet the Press," "I am absolutely comfortable with the fact that men marrying men, women marrying women and heterosexual men and women marrying one another are entitled to the same exact rights, all the civil rights, all the civil liberties."
The White House immediately clarified that Biden was not acting as a surrogate for President Barack Obama during the interview, nor was he expressing a change in policy within the administration.
Obama's views on same-sex marriage have been "evolving," he has said, though he already endorsed civil unions, according to The New York Times. Gay rights advocates have been increasingly frustrated with the president's refusal to take a clear stance on the issue, and some suggest his reluctance stems from concern of a backlash from more conservative and vital swing states during the upcoming elections.
Obama's stance in 2010 was, "My baseline is a strong civil union that provides them the protections and the legal rights that married couples have," according to The Times.
Richard Socarides, a former White House aide who advised former President Bill Clinton on gay rights said, "Trying now to walk this back will only hurt them." He added, "You can’t clarify an answer as direct and candid and expansive as the one he gave," according to The Times.
The latest CNN/ORC International Poll found that a majority of Americans (53 percent) believed that marriages between same-sex couples should be recognized, while 45 percent disagreed.