If I'm Lucky(1946)

Out of work swing band maneuvers a gig working for a political campaign, by drawing in and entertaining prospective voters at rallies. The candidate is really a stooge for a corrupt political machine, which discovers the band's handsome and appealing singer would make a better stooge. Meanwhile, romance blossoms between the band's singers. When election day approaches, the band's singer wants out of the campaign, but the machine threatens to smear him and his pals in the band if he quits.