WASHINGTON — Tom Steyer, the billionaire investor and activist, said Tuesday he’s 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 President Donald Trump’s impeachment. He surprised many Democrats in January when he traveled 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, of 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.

“The other Democratic candidates for President have many great ideas that will absolutely move our country forward, but we won’t be able to get any of those done until we end the hostile corporate takeover of our democracy,” Steyer said in a statement.