As they fight to be elected — or keep their seats of power — politicians this year are finding vastly different receptions to their musical strategies. That’s often been the case, as candidates and incumbents tap the celebrity endorsements and zeitgeist that music can confer a political campaign. Songs help define the tone — think Bill Clinton’s frequent use of Fleetwood Mac’s “Don’t Stop Thinking About Tomorrow” since 1993 – but they also subtly link the artist to the politician, whether the song was personally approved by the artist or not. “Music is essential to my political career,” said Democrat John Hickenlooper, the former Colorado governor and Denver mayor who’s battling Republican incumbent Cory Gardner for a U.S.