Billionaire US investor and activist Tom Steyer is joining the race for the Democratic presidential nomination, reversing course after deciding earlier this year that he would forgo a run.
Steyer, 62, is one of the most visible and deep-pocketed liberals advocating for US President Donald Trump's impeachment.
He surprised many Democrats in January when he travelled to Iowa, home to the nation's first presidential caucus, to declare that he would focus entirely on the impeachment effort instead of seeking the White House.
Since then, Steyer, from California, has said he's grown frustrated at the pace at which the Democratic-controlled House is approaching Trump.
Roughly half of the Democratic presidential contenders, seeking to appeal to the party's progressive base, have called on House Democrats to start an impeachment inquiry.
But Speaker Nancy Pelosi has resisted, warning that Democrats need to collect the facts and that a rush to impeachment could ultimately help Trump politically.
Despite becoming a national voice on the impeachment issue, Steyer made no mention of it in his campaign announcement.
Instead, he said his campaign will focus on reducing the influence of corporations in politics. He also plans to target climate change, which is the focus of the Steyer-backed advocacy group NextGen America.
Steyer said he would spend at least $US100 million on his campaign, a figure that was first reported by The New York Times.
Steyer joins the race three weeks before the next presidential debates , and he could struggle to get a spot on the stage.
He said he does not expect to qualify for the second Democratic presidential debates, which will be held July 30-31 in Detroit.
There are 20 spots at the debate for a field that includes two dozen candidates . If more than 20 people qualify, the Democratic National Committee will hold a tiebreaker to determine who gets on stage.
