Massachusetts Sen. Elizabeth Warren praised the victorious Biden for “running on the most progressive economic and racial justice platform of any general election nominee ever.” His choice of Ronald Klain as chief of staff was “excellent,” Minnesota Congresswoman and “Squad” member Ilhan Omar tweeted. And each of his Cabinet nominees, noted The Intercept’s Ryan Grim, is “more progressive and less entrenched with Wall Street” than their predecessor under President Barack Obama.

Perhaps the fullest articulation of this new Biden optimism comes from Saikat Chakrabarti, the firebrand organizer who co-founded Justice Democrats — the three-year-old group known for primarying centrist incumbents of its own party — and then became chief of staff to Congresswoman Alexandria Ocasio-Cortez. In his current role as president of progressive think tank New Consensus, Chakrabarti issued a supportive memo to President-elect Biden, encouraging him to go big on his plans for economic development.

“Biden ran a historically progressive campaign in terms of what he talked about doing. His whole ‘build back better’ plan talks about a multitrillion-dollar project of rebuilding America’s economy,” says Chakrabarti. “Politically, I think it’s very smart. What makes me optimistic is the fact that he even campaigned on this.”