President Barack Obama's re-election campaign intensified its rebukes of Mitt Romney Friday evening for a remark made by the presumptive Republican nominee about the president's birth certificate earlier in the day.

Speaking to a crowd of enthusiastic supporters in Commerce, Mich. -- and noting the local roots shared by him and his wife, Ann -- Romney quipped that "no one's ever asked to see my birth certificate. They know that this is the place that we were born and raised." Of course, Obama's birthplace has been the subject of fervid (if wholly debunked) conspiracy theorizing in the years since he arrived on the national stage.

The Obama campaign responded with a 15-second attack ad posted to YouTube Friday evening -- titled "America Doesn't Need A Birther-in-Chief" -- that recycles video of Romney's joke, while a narrator intones, "Holding out hope Romney had a vision for the middle class? Think again."

"Embracing unfounded conspiracy theories, distracting from real issues. America doesn't need a Birther-in-Chief," the voiceover continued.

The ad is the latest in a string of responses from the Obama camp to Romney's comment. First, a campaign spokesman slammed the Republican for "embrac[ing] the most strident voices in his party instead of standing up to them." Later, the president's official Twitter account followed with a barely veiled reference to the joke. The campaign also sent a fundraising email to supporters, with the subject line: "A new low for Mitt Romney."

Romney since insisted that he harbors no illusions about Obama's birthplace, telling a CBS News reporter that, "there's no question about where he was born. He was born in the U.S."

"This was fun about us, and coming home," Romney went on to say.

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  • Bo Obama

    President Obama pets the family dog, Bo, upon his return to the White House on March 15, 2012.

  • Bo Obama

    President Obama laughs as his dog Bo sniffs another dog as he shops at Petsmart on Dec. 21, 2011, in Alexandria, Va.

  • Bo Obama

    The Obama family dog Bo inspects the White House Christmas tree after its arrival at the White House on Nov. 25, 2011.

  • Bo Obama

    President Obama and first lady Michelle Obama read 'Chicka Chicka Boom Boom' to children during the White House Easter Egg Roll as Sasha Obama listens and dog Bo tries to get attention on the South Lawn of the White House on April 25, 2011. About 30,000 people were expected to attend the 133-year-old tradition of rolling colored eggs down the White House lawn.

  • Bo Obama

    In this photo provided by the White House, Bo, the Obama family dog, peers into the Oval Office from the colonnade, on Oct. 26, 2010.

  • Bo Obama

    White House horticulturist Dale Haney, left, washes off Bo's paws outside the White House on Oct. 19, 2010. The First Dog, Bo, was a gift from Sen. Ted Kennedy to Sasha and Malia who had been promised a dog by President Obama when he was on the presidential campaign trail.

  • Bo Obama

    A White House staff walks First Dog Bo as President Barack Obama lands at the Cape Cod Coast Guard Air Station in Cape Cod, Mass., on Aug. 19, 2010, to leave for Martha's Vineyard for a family vacation.

  • Bo Obama

    The Obama family dog, a Portuguese water dog named Bo, trots across the South Lawn Aug. 2, 2010.

  • Bo Obama

    President Obama, first lady Michelle Obama and their daughters Malia, left, and Sasha, right, walk with their dog Bo as they visit the Bass Harbor Head Light lighthouse during the first family's weekend vacation in Bar Harbor, Maine, on July 17, 2010.

  • Bo Obama

    President Obama walks the first dog Bo to a picnic for members of Congress on the South Lawn of the White House June 8, 2010.

  • Bo Obama

    President Obama takes a walk down the street from his home accompanied by his mother-in-law Marian Robinson, daughters Malia Obama, left, and Sasha Obama, right, and dog Bo May 29, 2010 in Chicago.

  • Bo Obama

    Clockwise from top, President Obama, first lady Michelle, first dog Bo, daughters Sasha and Malia, and Marian Robinson, mother of Mrs. Obama, walk down the stairs from the Truman Balcony during the annual White House Easter Egg Roll at the South Lawn April 5, 2010.

  • Bo Obama

    President Obama's family dog Bo waits for the president on March 5, 2010.

  • Bo Obama

    President Obama's family dog Bo nuzzles the cast on a boy's leg during a visit to the Children's National Medical Center on Dec. 22, 2009.

  • Bo Obama

    Bo, the Obama family dog, sits in the snow outside of the Brady Briefing Room of the White House on Dec. 19, 2009.

  • Bo Obama

    A miniature Bo, President Obama's dog, a part of the official White House gingerbread house, designed by White House Pastry Chef Bill Yosses, displayed in the State Dining Room of the White House during a press preview of holiday decorations on Dec. 2, 2009.

  • Bo Obama

    In this handout photo provided by the White House, Cappy, the brother of Obama family dog, Bo, eats treats at a birthday celebration for Bo in the Rose Garden of the White House on Oct. 9, 2009.

  • Bo Obama

    First lady Michelle Obama hands the family dog Bo to her husband President Barack Obama as they leave a school in D.C. on Sept. 26, 2009, where their daughter Malia played a soccer game.

  • Bo Obama

    President Obama is greeted by his daughters Sasha, center, Malia and their dog Bo upon his return to the White House on Sept. 15, 2009, following a trip to Ohio and Pennsylvania.

  • Bo Obama

    The Obamas welcome Bo, a six-month old Portuguese water dog and a gift from Sen. Ted Kennedy to Sasha and Malia.

  • Bo Obama

    Bo arrived at the White House wearing a lei on Easter Sunday in 2009.

  • Bo Obama

    Bo, the Obama family dog, lounges in the West Garden Room of the White House, Sept. 15, 2011.

  • Bo Obama

    President Obama and Bo, the Obama family dog, ride in the presidential motorcade en route to PetSmart in Alexandria, Va. The president bought Bo some Christmas gifts at the pet store then walked nearby to Best Buy to purchase gifts for his daughters.

  • Bo Obama

    President Obama plays with Bo, the Obama family dog, aboard Air Force One during a flight to Hawaii, Dec. 23, 2011.

  • Bo Obama

    White House Deputy Director of Oval Office Operations Brian Mosteller attempts to protect his shoes as he plays with the Obama family dog Bo in the Cabinet Room at the White House April 21, 2009.

  • Bo Obama

    The Obama family dog, Bo, lies on a carpet in the White House on July 27, 2009.

  • Bo Obama

    President Obama looks back as Bo, the Obama family dog, follows him into the Oval Office on Jan. 27, 2012.

  • Bo Obama

    Bo relaxes in the doorway of in the Oval Office, Sept. 14, 2009.