Newt Gingrich is on the attack against Mitt Romney, over his work at Bain Capital, over his record as Massachusetts and now over how he treats his pets.

A web  ad released today by the Gingrich campaign revives the story of a Romney family road trip 25 years ago during which Romney strapped a dog carrier, with the family's Irish setter Seamus inside, to the roof of his station wagon for the 12-hour drive from Boston to Ontario, Canada.

Word of Romney's dog-on-the-roof, road-trip seating chart infuriated animal activists and pet owners during his 2008 White House bid after a Boston Globe story detailed the incident.

At a campaign event in South Carolina last week, a protester with a sign that read " Dogs Against Romney" greeted Romney supporters while standing next to a car with a stuffed animal dog strapped to the roof.

"This is a completely air-tight kennel, mounted on the top of our car," Romney says in the ad, defending his dog placement in a Fox News clip. "He was in a kennel at home a great deal of time as well. It was where he was comfortable."

The video then shows white words flashing across a black screen: "Imagine what Obama would do with a candidate like that."

The ad, titled "For the Dogs," includes six other clips of Romney's most often-cited verbal gaffes including his "corporations are people too" argument at the Iowa state fair, his "I like to fire people" statement earlier this week  nd his "$10,000 bet" from a GOP debate last month. As of now, the ad will not air on television, Gingrich spokesman RC Hammond said.

Gingrich and Romney are squaring off for an ad battle royale in South Carolina. Super PACs supporting the two candidates have announced ad buys that total a combined $5 million in the Palmetto State .