Des Moines, Iowa (CNN) - A political action committee supportive of Mitt Romney posted an ad blasting Newt Gingrich Thursday night, then abruptly took down the spot.
The Restore Our Future ad hit Gingrich for his "baggage," including ethics violations and his past stance on climate change. The ad said Democrats had been attacking Romney in the hopes of a general election match-up against Gingrich.
A spokeswoman for the group would not give details on the negative ad, telling CNN: "We're not commenting. It's an unfinished ad."
The spot was posted hours after the super PAC released its first ad targeting Obama and showing Romney in a positive light.
Restore Our Future cannot communicate with the Romney campaign on strategy because of campaign finance rules.
Gingrich's campaign responded to the ad Thursday night.
“This won’t be the first, this won’t be the last. There’s going to be an awful lot of them and none of them are going to work,” said Gingrich press secretary R.C. Hammond.
The ad was posted as Gingrich appears to be gaining a solid lead in polls in several early voting states. Two Romney surrogates harshly criticized the former House speaker in a conference call with reporters Thursday.
At a campaign event in South Carolina, Gingrich told reporters: "We're going to stay positive."
- CNN's Shawna Shepherd and Kevin Bohn contributed to this report.