Former Massachusetts governor Mitt Romney leads President Obama by six points among registered voters in Florida, according to a new Quinnipiac survey, a marked change from two months ago that, the poll suggests, could be linked in part to Obama’s recent statements in support of gay marriage.

Romney, the presumptive nominee, was ahead of Obama 47 percent to 41 percent, according to the poll. Choosing Sen. Marco Rubio (R-Fla.) as his running mate would give Romney a 49 to 41 percent lead.

A month ago, Romney and Obama were tied in the state; in March Obama led by 7 points. The downward slide, in a critical swing state in what is expected to be an extremely close election, is not good news for the president.

While Obama continues to have a wide lead over Romney on likability, the Republican candidate’s favorability ratings are higher. Fifty percent of voters have an unfavorable view of the president, compared to 35 percent who have an unfavorable view of Romney.

Romney is also viewed as better able to handle the economy, 50 percent to 40 percent.

The president is winning only 33 percent of white voters, compared to 85 percent of black voters and 45 percent of Hispanic voters. Women, who have given Obama an edge in previous swing-state surveys, are evenly divided in this poll, while men break for Romney 50 to 37 percent.

The poll also suggests gay marriage could be an issue in the race.

Twenty-five percent of voters, including 23 percent of independent voters, say Obama’s support of gay marriage makes them less likely to support his candidacy. Only 11 percent say it makes them more likely to support the president.

Nineteen percent of voters say Romney’s opposition to same-sex marriage makes them less likely to vote for him, compared to the 23 percent who say it makes them more likely to vote for him.

Nationwide, however, a new Washington Post-ABC News poll shows that public opinion continues to shift in favor of same-sex marriage. And a majority of Americans — 55 percent in the Post poll — continue to say the issue will not be a major factor when they go to the polls.

Quinnipiac surveyed 1,722 registered voters from May 15 to 21, with a margin of error of 2.4 percentage points.