Minnesota Democratic Rep Dean Phillips announced the end of his quixotic primary challenge against President Joe Biden after a demoralising Super Tuesday result.

       “I’m going to suspend my campaign, and I will be right now endorsing President Biden. The choices are so clear ... we only have two of them, and it’s going to be Donald Trump or Joe Biden,” Mr Phillips said on Wednesday in a radio interview.

       Mr Biden dominated the primaries on Super Tuesday, when 15 states voted, including a sizable victory in Mr Phillips’s home state of Minnesota.

       The Democratic challenger had earned no delegates after Super Tuesday, compared to the president’s 1,497 delegates.

       On Tuesday evening, he wrote on X: “Congratulations to Joe Biden, Uncommitted, Marianne Williamson, and Nikki Haley for demonstrating more appeal to Democratic Party loyalists than me.”

       Mr Phillips’s announcement comes hours after Nikki Haley, the last-standing Republican challenger against former president Donald Trump, also announced her exit from the race. She said she had “no regrets” but refused to endorse Mr Trump for president.

       Although the Minnesota Democrat endorsed the president on Wednesday, for months he has criticised the 81-year-old’s re-election bid, blasting his age and disapproval rating among voters.

       “I know this campaign is a long shot, but that is why I think it is important and worth doing,” Mr Phillips previously conceded.

       Despite his failed presidential bid, Mr Phillips has boasted an impressive record of success. He defeated a six-term Republican in 2018, making him the first Democrat to flip the Republican district since 1958.