Campaign 2012 may be unpredictable, but you can be certain of one thing: Republicans will get in trouble for unauthorized use of hit songs.

When Michele Bachmann used Tom Petty’s “American Girl” at a kickoff campaign rally on Monday, the singer was none too happy. According to the Star Tribune, he’s sent a cease and desist letter to stop playing his 1977 classic.

This is not the first time that a campaign has run afoul of public performance copyrights, and it isn’t even the first time the Petty has tried to put a stop to it. He balked at George W. Bush’s use of “I Won’t Back Down” at campaign events in 2000.

Republicans complain that they are the ones usually targeted by musicians, part of an industry that leans to the left. And they may be right. Hillary Clinton, after all, used “American Girl” in her campaign as well.

That’s because artists are also concerned about false endorsement, or the impression that voters may have that a politician has received permission, and therefore approval of their political stances, by a songwriter or singer.

In 2008, Jackson Browne, a supporter of candidate Barack Obama, sued John McCain for using “Running on Empty” in a campaign ad. As it turned out, the spot was run by the Ohio Republican Party, but the suit ended in what sources said was a six figure settlement with the Republican National Committee.

Last year, Don Henley won a judgment against Chuck DeVore, a candidate for U.S. Senate in California, for using a takeoff of “Boys of Summer” and “All She Wants to Do Is Dance” in campaign web videos. DeVore had defended the videos as a parody, and therefore a fair use of copyrighted work. But the federal judge didn’t buy it.

And earlier this year, David Byrne reached a settlement with former Florida Gov. Charlie Crist after Crist used “Road to Nowhere” in a campaign advertisement. The settlement amount was undisclosed, but part of it was a videotaped apology from Crist, posted on YouTube, that has the feel of a hostage reading off a statement on demand of his captors.

So why does this keep on happening?

“They just think music is free like a lot of other people on the planet,” says Lee Phillips, senior partner at Manatt, Phelps & Phillips in Los Angeles.

What happens is that campaigns want a song that gets attention — and may be thinking of that above all else.

Phillips represents Steve Perry of Journey, which has been especially conscious of who is playing there music and where. Especially popular has been the 1981 hit “Don’t Stop Believin,” which has undergone a revival ever since it was used in the 2007 finale of “The Sopranos.” The song seems especially suited to a political campaign — but Perry and Journey were none too pleased when they got word that Newt Gingrich had used it at an event. Their attorneys sent a cease and desist letter.

Usually, that is it. But the legal issues can change, or get murkier, when a campaign has obtained an ASCAP license to play an array of different hits. Then, artists tend to rely on the argument that the campaign is giving the impression of an implied endorsement.

“Our position is that you are tying in the performer with the politician’s position, and that is a false endorsement,” Phillips says, adding that it is a “personal choice to the people who own the song.”

Usually, the campaign stops the use of a song in public performances. But the situation gets more complex when a song is used as part of an ad or web video. In April, Journey’s legal team filed suit against Adalah NY, a pro-Palestinian group that organized a “flash mob” at Grand Central Station in which activists sing and dance to a variation of the music, “Don’t Stop Boycottin.” The YouTube version became a viral hit.

Lawyers also have gotten more adept at sending out “cease and desist” notices quickly. They may be mindful of the example from 1988, when Bobby McFerrin’s “Don’t Worry, Be Happy” became an anthem of George H.W. Bush’s campaign before the singer publicly expressed his displeasure, ordered them to stop and even dropped it from his concert playlists.

Phillips has his own idea for campaigns: Write some original music. He knows it takes time and doesn’t get the attention, but it’s been done before. And thank God it has, because otherwise we wouldn’t have 1972’s “Nixon Now,” below.

Update: As of today, the Bachmann campaign is still playing the song.