Tom Steyer launches 2020 campaign after saying he wouldn't

FILE - In this March 13, 2019, photo, billionaire investor and Democratic activist Tom Steyer speaks during a "Need to Impeach" town hall event in Agawam, Mass. Steyer announced Monday, June 24 that he will put $1 million toward registering millennial voters in Virginia. Steyer's liberal advocacy group, NextGen America, will engage young voters in Republican-held districts in the hopes of flipping the Republican-led General Assembly to the Democrats in November. (Source: AP Photo/Steven Senne, File)

WASHINGTON (AP) -- Billionaire 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 made the announcement Tuesday, casting himself as an outsider who will oppose what he calls "the hostile corporate takeover of our democracy."

The 62-year-old from California 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 declared he would focus entirely on the impeachment effort instead of seeking the White House.

Since then, Steyer has said he's grown frustrated at the pace at which the Democratic-controlled House is approaching Trump.

Despite becoming a national voice on the impeachment issue, Steyer made no mention of it in his campaign announcement.