The consolidation of left-wing support is a remarkable turnaround for Sanders. In September, the Working Families Party became the first major national progressive group to endorse a candidate when it picked Warren — despite siding with Sanders in 2016. Warren was surging at the time, and looked poised to overtake Sanders as the leader of the progressive movement and a frontrunner for the nomination.

But now it’s Sanders with the wind at his back. The endorsements, on display here Sunday when Rep. Rashida Tlaib and the Sunrise Movement joined him for a rally attended by more than 900 people, are giving him a jolt of momentum weeks ahead of the Iowa caucuses and supplying him with fresh volunteers in key areas.

“I’m not surprised that Bernie is increasingly consolidating support,” said Waleed Shahid, an aide for the left-wing group Justice Democrats, which has not yet endorsed a candidate. “Many of his staff have backgrounds in community organizing, his 2016 campaign helped grow the progressive movement, and he received [Rep. Alexandria Ocasio-Cortez’s] endorsement, who is shaping the future of the progressive left in significant ways.”