"My view is that marriage itself is between a man and a woman," the presumptive Republican presidential nominee told reporters. He said he believes that states should be able to make decisions about whether to offer certain legal rights to same-sex couples.
"This is a very tender and sensitive topic, as are many social issues, but I have the same view that I've had since — since running for office," Romney said. He first ran for political office in 1994, when he challenged Sen. Edward M. Kennedy, D-Mass., and was elected governor of Massachusetts in 2002.
Obama is the first president in history to support gay marriage. Polls show the country is evenly divided on the issue.
Romney did not go so far as to accuse Obama of changing his position on gay marriage, though the president has said that he had an "evolving" view of the subject. Questioned by reporters, Romney said news reports indicate Obama has shifted his stance.
Romney was a leading voice against gay marriage as Massachusetts governor. The courts legalized gay marriage in the state during his tenure, but he supported a constitutional amendment to define marriage as the union of a man and a woman.
After gay marriage became legal, Romney sought to enforce a statute banning state officials from marrying gay couples from other states. In a speech to conservatives last winter, Romney touted that move, saying he prevented Massachusetts from becoming the "Las Vegas of gay marriage."
Romney said Wednesday he supports limiting benefits for same-sex couples.
"I do not favor civil unions if they are identical to marriage other than by name," he told the Fox TV station in Denver. "My view is the domestic partnership benefits, hospital visitation rights, and the like are appropriate but that the others are not."
The Romney campaign did not respond to requests for clarification about which benefits Romney supports and which he does not.
Romney also faced an internal issue this month when his openly gay national security spokesman, Richard Grenell, resigned after his support for gay marriage drew intense criticism from conservatives.
Grenell, who served as spokesman for then-U.N. Ambassador John Bolton during the Bush administration, said in a statement that Obama is on the "the right side of history," though he suggested the president is playing politics with civil rights.
A new Associated Press-GfK poll shows independent voters trust Obama over Romney to handle social issues "such as abortion and same-sex marriage," with 39 percent favoring Obama and 22 percent favoring Romney. A majority of voters trust Obama over Romney in every age group except senior citizens.
While conservative Republicans trust Romney over Obama by wide margins, moderate and liberal Republicans are almost evenly split between Obama and Romney.