ST. LOUIS • When it comes to one of the latest ads attacking his presidential primary rival, Mitt Romney borrows from the playbook of an unlikely source — although it remains unseen whether he will get away with it.

Over the weekend, Romney's campaign began running an ad in Florida that uses an old news clip to take a swipe at the resurgent Newt Gingrich.

The 30-second spot is made up almost entirely of a 1997 NBC news report, with anchorman Tom Brokaw discussing an ethics fine levied against Gingrich when he was speaker of the U.S. House.

To Missouri voters, this tactic should sound familiar.

In 2010, Democratic Senate hopeful Robin Carnahan performed an identical maneuver, using a 2006 clip of Fox News personality Chris Wallace questioning Republican Roy Blunt's credentials to become GOP Majority Leader in the House, a role he ultimately fell short of capturing.

Fox News sued the Carnahan campaign, alleging copyright infringement and misappropriation of Wallace's likeness. 

The lawsuit was settled after the election, but the cost of fighting the suit was more than $85,000, leading Carnahan to seek to form a legal defense fund after she had already lost the election.

Carnahan's campaign had argued that use of the Fox News clip was covered under the "fair use" doctrine of copyright laws. But, as part of the settlement with Fox, the campaign acknowledged the use of the news clip in the ad "exceeded that which is permitted."

In Florida, Romney's campaign has also argued their use of the NBC news clip is considered fair use.

However, after both an NBC attorney and Brokaw himself expressed concerns about the ad, Romney has agreed to meet with the network.

If he looks at the Carnahan case, Romney may conclude that his chances of succeeding on the legal merits is unlikely, and he very well may end up taking the ad down to avoid a lawsuit. 

By then, though, the ad and the spat with NBC would have attracted enough ink that, even if the commercial is taken down prematurely, it would have achieved exactly its aim, or close to it.