Environmentalist Tom Steyer, whose fortune tips the scales at well over $1 billion, has changed his mind and now plans to join the Democratic Party field in the race for president.

Politico reported Monday that Steyer has indicated to people close to him that he has changed his mind about 2020 and will run for the White House.

Steyer has spent millions of dollars over the years supporting Democrats running for office. A resident of San Francisco, Steyer is worth an estimated $1.6 billion, according to Forbes.

Steyer has been highly critical of President Donald Trump and has contemplated running for president during the current campaign cycle, but in January he ruled it out.

It’s not clear what prompted Steyer’s change of heart on running.