"Even though this campaign didn't have the conclusion we were hoping for, every moment of it has been worthwhile," Hickenlooper said in a statement on Thursday, Xinhua reported.
Hickenlooper signaled that he will consider running for the U.S. Senate to unseat Republican incumbent Cory Gardner.
Opinion writer Jennifer Rubin applauded Hickenlooper's exit, saying downsizing his party's crowded candidate field can help Democratic voters decide on the best person to run against U.S. President Donald Trump in the presidential race.
Hickenlooper announced his candidacy in March, striking a moderate tone among his Democratic opponents. He emphasized on his successful administrative record in Colorado on the campaign trail, but after two appearances on national debate stages, his campaign was lagging behind in securing the poll and donor numbers needed to put him through the third round of debate.
Hickenlooper, 67, previously served as the mayor of Denver and the governor of Colorado.