Bernie Sanders has officially ended his bid for the presidency and endorsed Joe Biden. Most of his other former Democratic challengers have now thrown their support behind him too. 

But will Biden be able to earn the support of progressive voters and unify the party — and could climate be the lynchpin issue that wins their favor?

We spoke to someone who knows a thing or two about this: Former Presidential Candidate and billionaire Tom Steyer. He tells us what he's learned about prioritizing climate during the 2020 race — and how his money will continue to wield its influence.