US Representative Eric Swalwell has become the first major candidate to drop out of the Democratic presidential race, ending a long-shot bid fuelled in part by his efforts to investigate Republican President Donald Trump.
He plans to run for re-election to Congress in his California district.
Mr Swalwell said he was not prepared to make an endorsement in the crowded Democratic contest for the right to face Mr Trump in the November 2020 presidential election.
Democratic presidential candidate Eric Swalwell challenged frontrunner Joe Biden on the second night of the first Democratic debates Source: ABACA
He was one of the more aggressive candidates on the Democratic debate stage last month, challenging former Vice President Joe Biden, 76, to "pass the torch" to a younger generation.
But the approach did little to improve his standing in opinion polls among the more than 20 Democrats seeking the party's nomination. He was in jeopardy of falling short of the qualification requirements for the next round of debates later this month.
Mr Swalwell has raised his profile in recent years by becoming a staple on cable television news, especially to talk about investigations of the Trump administration. But he consistently trailed in 2020 presidential polls.
Mr Swalwell was one of the youngest candidates vying for the Democratic nomination, along with Pete Buttigieg, the mayor of South Bend, Indiana, 37, and US Representative Tulsi Gabbard from Hawaii, 38.
The minimum age to serve as US president is 35.
