Sanders left in the cold after Warren ends campaign

WASHINGTON－It took Joe Biden's moderate rivals just hours to unite behind his presidential campaign after they left the race. Bernie Sanders hasn't been so fortunate.

Elizabeth Warren, one of Sanders' closest ideological allies, declined to endorse anyone after suspending her campaign on Thursday. She didn't rule out an endorsement of her New England neighbor but said she wanted to "take a deep breath and spend a little time on that".

High-profile Warren supporters across the country, particularly women, were also hesitant to race into Sanders' camp. And on Capitol Hill, where Biden was racking up new endorsements daily, the Vermont senator hasn't earned a single new endorsement, even among the most progressive elected officials, in two weeks.

The dangerous silence from Warren and progressive officials across the country came at the worst time for Sanders, who's suddenly losing momentum in a two-man race with the former vice-president as another set of high-stakes primary elections looms. Sanders is moving forward with the same coalition that was beaten soundly earlier this past week. And if he cannot find a way to grow, and grow quickly, the Vermont senator's 2020 challenge will only become more dire.

Within the campaign, some lament Sanders' unwillingness to court elected officials as Biden's coalition grows exponentially. The former vice-president earned endorsements over the past week from three former rivals just hours after they suspended their campaigns: Pete Buttigieg, Amy Klobuchar and Mike Bloomberg. Another, former Texas representative Beto O'Rourke, also endorsed Biden on the eve of Texas' primary, which Biden narrowly won.

Biden's team has already announced plans to dispatch Klobuchar, a Midwestern moderate, to Michigan ahead of the state's critical primary election on Tuesday.

Wait-and-see approach

Many would-be Sanders supporters, meanwhile, are taking a wait-and-see approach.

Adam Green, the co-founder of the Progressive Campaign Change Committee, said the organization would ultimately endorse whomever Warren does.

"We are among her many supporters who are rooting for her to exert every ounce of leverage she has in this moment of goodwill in order to advance the big ideas and the people she cares so much about," Green said on Thursday.

He said Warren, a former Harvard law professor and expert on the legalities of contracts, would approach the decision carefully and that process "might be time-intensive or it might not be."

The National Organization for Women, whose political action committee endorsed Warren earlier in the past week, encouraged Warren to take her time. In an interview, NOW President Toni Van Pelt urged Warren not to endorse Sanders.

"She has a lot of leverage right now. We do trust her to make the right decisions on how to proceed. But we'd like her not to rush into this," Van Pelt said.

Sanders has the public support of nine members of Congress, yet he has earned no new endorsements since Feb 20. Biden has won at least 26 this week alone.

One of Sanders' few allies in Congress, Representative Ro Khanna, said on Thursday that Warren's support would be "a game-changer". "But that's her decision to make," he said.