NASHUA, N.H. — Massachusetts Gov. Mitt Romney, a possible presidential candidate in 2008, has received a special invitation — to attend the elevation of Boston Archbishop Sean O'Malley to cardinal at the Vatican.

The trip to Rome next week is further evidence of a growing relationship not only between Romney and the local leadership of the Roman Catholic Church but also of the importance of Catholics and social conservatives in the campaign that Romney is contemplating.

The Republican governor recently filed a bill that would allow a Catholic social service agency to deny adoptions to gay couples.

"This is extraordinary and particularly for someone of my faith," said Romney, a Mormon, before he spoke at a St. Patrick's Day breakfast in New Hampshire, an early presidential state. "I don't know that there's ever been a Mormon guy that's been to the Vatican for a Mass held by the pope, so it's a personal honor."

He denied seeking any political gain from the trip, saying he was invited, along with Boston Mayor Thomas Menino, only because of his office, not his politics.

In another sign he is strongly considering a White House bid, Romney sat down recently with C-SPAN for an hourlong interview that will air Sunday night.

He agreed that his father's 1968 campaign for the Republican nomination for president may have been doomed when the elder Romney, then the governor of Michigan, said he had been "brainwashed" by military leaders and diplomats during a trip to Vietnam in 1965. That, the elder Romney contended, accounted for his earlier support for the war.

Mitt Romney, however, argued that his father was later proven right in his antiwar views.

"His point was that (Defense Secretary Robert) McNamara and (President Lyndon) Johnson had been lying to the American people, and . . . in the past he had swallowed, hook, line and sinker, what he had been told by military generals," Mitt Romney said.

"I remember that when McNamara came out with his book . . . and admitted that he had lied to the American people, my dad took a certain degree of satisfaction in the fact that the people now knew that what he said was true," Romney added. "And he used to say that in politics being right too early is not a good thing. But he was right, and it was too early."

In 1968, while serving as a Mormon missionary in France, Romney was involved in a car crash and wrongly declared dead by French police. His father asked Sargent Shriver, the U.S. ambassador to France, to investigate.