Politicians have been using music in political campaigns for years, and are typically obliged to use whatever songs they want as long as they pay a blanket license fee. This hasn't stopped liberal musicians from demanding that Republican candidates stop using their songs without permission, and taking legal action for misrepresenting their work or breaking copyright laws. At this point, any major Republican is doomed to getting cease-and-desist letters from pop stars unless they take the path of least resistance and go with a song by a relatively small pool of Republican rockers. This is exactly what Mitt Romney has done, by the way - his current campaign theme is "Born Free" by the famously right-leaning Kid Rock.
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