At the height of the nasty GOP primary fight between Newt Gingrich and Mitt Romney there was always the expectation that the attacks could come back to haunt them.  And now they have.

Today, as Gingrich formally withdraws from the presidential race, the Obama campaign has released a "greatest hits" reel of Gingrich attacks on Romney, all playing directly into the Democratic story line of the former governor as a dishonest, secretive, out of touch American.

The opening scene shows Gingrich on CNN's "Piers Morgan Tonight":  "As a man who wants to run for president of the U.S. who can't be honest with the American people, why should we expect him to be honest about anything if he's president?"

The minute and a half video - titled "Newt Gingrich: Frankly, not Mitt Romney's biggest supporter" - features the former House speaker lashing Romney's business record at Bain Capital; criticizing his lack of transparency - citing the Swiss bank account - and harsh immigration plan; and even doubting Romney's ability to inspire people.

"Are you calling Mitt Romney a liar?" CBS' Norah O'Donnell asks Gingrich in the final clip of the reel.

"Yes," Gingrich says.