Erik Underwood, a Denver Democrat who unsuccessfully ran for governor in 2018, announced Tuesday that he is running for U.S. Senate this year. Underwood, 40, is a former Republican and was a staffer for former U.S. Sen. George Voinovich, an Ohio Republican. He says his time in Washington showed him how to get things done. “I’m the only candidate who has ever worked in the United States Senate,” Underwood said of the large Democratic field.