Democratic megadonor and radical environmental activist Tom Steyer on Tuesday officially entered the crowded field for the 2020 Democratic presidential nomination.

Steyer is best know for launching the political organization NextGen America, which has raised and spent hundreds of millions of dollars on progressive issues throughout the country. His political activism has ranged from funding carbon tax campaigns and renewable energy mandates to his “Need to Impeach” initiative which has poured millions into a lobbying effort aimed at convincing lawmakers to impeach President Trump.

In the 2018 elections, Steyer fronted a $15.2 million failed effort to establish a carbon tax in Washington State and spent nearly $18 million trying to pass a renewable energy mandate in Arizona, a campaign which also ended in defeat. Both of these efforts would have raised household energy prices for consumers while disproportionately impacting poor Americans who spend a greater share of their income on energy than wealthier Americans.

Steyer has also praised Rep. Alexandria Ocasio-Cortez’s Green New Deal resolution, calling it “extremely successful” and said Rep. Ocasio-Cortez deserves “enormous credit” for introducing the Green New Deal.

In his announcement, Steyer pledged to focus his campaign on climate change and to spend at least $100 million on his campaign.