COMMERCE, Mich. — During a homecoming rally in his boyhood state of Michigan on Friday, Mitt Romney thrust himself into a controversy over President Obama's birthplace that has roiled at the fringe of his party, joking: "No one has ever asked to see my birth certificate."

Though Obama's aides have produced both the short and long form of his birth certificate — showing that he was born in Honolulu — critics of Obama have raised questions about his citizenship since the early days of the 2008 election. Romney has insisted he believes the president was born in the U.S., and his advisers have said efforts by Donald Trump and others who fan the flames of that controversy have been a distraction.

But before thousands of supporters that gathered for a rally with Romney and his vice-presidential candidate, Rep. Paul Ryan, outside Detroit at the Long Family Orchard, Farm & Cider Mill, Romney appeared to make an oblique reference to the debate when he was detailing his roots in Michigan, where his father was a three-term governor in the 1960s.

"I love being home in this place where Ann and I were raised, where both of us were born," Romney said after an emotional introduction by his wife, who spoke of her father-in-law's tradition of service.

"Ann was born at Henry Ford Hospital. I was born at Harper Hospital. No one's ever asked to see my birth certificate," he continued, as the crowd roared with approval. "They know that this is the place where we were born and raised."

Romney did release his birth certificate in May.

After the comment, Romney returned to his standard stump speech, recounting his long courtship with Ann, and the Romney campaign sought to downplay the remark as an offhand comment.

"The governor has always said, and has repeatedly said, he believes the president was born here in the United States," Romney adviser Kevin Madden said. "He was only referencing that Michigan, where he is campaigning today, is the state where he himself was born and raised."

That was not the way that the Obama campaign, or Romney's crowd, interpreted the remark.

Obama spokesman Ben LaBolt said after Romney's birth-certificate comment that the presumed Republican nominee had "embraced the most strident voices in his party instead of standing up to them."

LaBolt criticized next week's lineup at the Republican National Convention in Tampa, Fla., which will include Trump and Arizona Sheriff Joe Arpaio, who have questioned Obama's citizenship.

"Gov. Romney's decision to directly enlist himself in the birther movement should give pause to any rational voter across America," LaBolt said.

Later Friday, the Obama campaign appeared to make light of Romney's remarks in a message sent from its Twitter account. "Song of the day: Born in the U.S.A."

Material from The Washington Post is included in this report.