(Charlie Neibergall | AP file photo) In this Aug. 10, 2019 photo, then Democratic presidential candidate former Colorado Gov. John Hickenlooper speaks at the Presidential Gun Sense Forum, in Des Moines, Iowa. Former Colorado Gov. Hickenlooper said Thursday, Aug. 22, that he will run for the U.S. Senate, becoming the immediate front-runner in a crowded Democratic field vying for the right to challenge Republican incumbent Cory Gardner.