Gov. Mitt Romney, elected a year ago on a pledge to reform state government and revive the Massachusetts economy, is suddenly enmeshed in a complicated, divisive moral debate, with the eyes of the nation and the world on him.

The gay marriage issue is not of his choosing; during last year's gubernatorial campaign, he took pains to finesse questions of gay rights, and such issues have hurt him previously in his political career. Now Romney is struggling to find a middle ground on a subject that polarizes voters, and he may find his political fortunes tied to how he handles the highest-profile issue he has faced thus far as governor.

"Governor Romney has an eye on the White House, and this presents an enormous obstacle from here to there," said Jeffrey Berry, a political science professor at Tufts University. "For the national Republican Party, the court's decision was a gift — Christmas came early. But not so for Governor Romney. He has a decision here that can affect the future of his career, and I don't think he's figured out what he's going to do."

Romney has sold himself as a moderate Republican, reaching out to independent and swing voters with middle-ground positions on abortion and health care for the poor, and by offering a low-tax, business-friendly message in a state dominated by Democratic elected officials. It worked in last year's election, as he succeeded in keeping social issues largely in the background.

The Supreme Judicial Court's ruling that same-sex couples are permitted to marry presents a minefield for a governor who is looking to establish a national Republican profile while not alienating the Democrats and independents whose support he needs to stay in office.

Romney has already begun staking out a centrist position in a debate prone to be defined by extremes. Barely an hour after the court's opinion was made public Tuesday morning, he delivered a nuanced, carefully prepared response that included elements to satisfy both ends of the political spectrum.

The governor denounced the court ruling and came out strongly against gay marriage, promising to work to amend the state constitution to ban such unions. He quickly added that he'll work with the Legislature on a "parallel" track to establish some rights for same-sex couples.

Wednesday, he repeated his position to a far wider audience, on NBC's "Today Show" and ABC's "Good Morning America."