Although other Republican candidates have backed down from lawsuits by singers, there's still an open legal question over whether permission needs to be attained from songwriters for the public performance of music.

In the past few years, there's been growing animosity over the way that Republican candidates for public office use music in campaigns. Today comes word of a new lawsuit filed against Newt Gingrich's campaign for using "Eye of the Tiger," the Grammy-winning song from Rocky III.

The new lawsuit, first reported by TMZ, was filed in Illinois federal court on behalf of Rude Music Inc., owned by Frank Sullivan, a co-author of the song. The complaint says that Gingrich has used the song without authorization at various conferences and campaign rallies. The plaintiff claims this is a violation of the song's copyright and demands an injunction to put a stop to Gingrich's choice of entrance music.

Gingrich isn't the first politician to be sued over music.

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After the 2008 election, singer Jackson Brown filed a lawsuit against John McCain over use of the song, "Running on Empty." A few months later, singer Don Henley brought legal action against California senatorial candidate Chuck DeVore over use of the songs, "Boys of Summer" and "All She Wants To Do Is Dance." And two years after that, songwriter David Byne sued Florida ex-governor Charlie Crist over use of the song, "Road to Nowhere."

In each of these cases, the politicians backed down and were forced to make public apologies. In Crist's case, it came in the form of an embarassing YouTube video.

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But all of these cases involved campaign advertisements, not political rallies. Last year, Tom Petty sent a cease-and-desist letter to Michele Bachmann's campaign for using "American Girl" as her entrance song as campaign stops, but a lawsuit never materialized.

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The question over the legality of playing music on the stump is one that hasn't yet been tested in the courts. Most political campaigns purchase blanket licenses from performance rights organizations such as ASCAP, and although the Gingrich campaign hasn't yet commented on the new lawsuit, it won't be surprising to see a defense of a copyright lawsuit being grounded upon the existence of a license.

Fair use could be a factor as well.

Although none of the above politicians who were previously sued over use of music were successful at the preliminary stages of their respective lawsuits, it's also true that none of the cases went to trial, and no appellate court has touched on whether politicians deserve broad free speech protections from copyright claims. Plus, political candidates continue to avail themselves of the "fair use" defense. For example, in response to allegations over the weekend by NBC that use of a Tom Brokaw clip was out-of-bounds, the Mitt Romney campaign argued "fair use."

One other factor potentially adds intrigue to the lawsuit by Rude Music against the Newt Gingrich campaign.

In September, the Chicago Sun-Times reported that Jim Peterik, the other songwriter of "Eye of the Tiger" had made a move to terminate his copyright grant.

In the article, Peterik is quoted as explaining how his business relationship with Sullivan worked. "Frankie and I share custody," he told the newspaper. "I gave him permission to use 'Eye of the Tiger' on Starbucks. I could have vetoed it. I didn’t. . ."

It's unclear whether Peterik is on board this latest legal action. His attorney wasn't immediately available for comment.

E-mail: eriqgardner@yahoo.com

Twitter: @eriqgardner