Interviews with nearly two dozen aides, allies, and progressive operatives over the last week reveal a campaign struggling to reconcile the reality of the delegate math with the emotions of an entire progressive movement that now rests on the shoulders of a man who has pursued his aims with a single-minded focus for more than 50 years, who built a vast and obsessive following from almost nothing in 2016, who doesn’t easily back down — even when he knows he’s lost.

“He was never able to expand his coalition,” said Mark Longabaugh, a top adviser who split with the campaign early last year over strategic disagreements with the candidate. “He just didn’t succeed at it.”…

Sanders spoke to Warren a “handful” of times throughout the week, a campaign aide confirmed, but she has declined to offer her endorsement.

Several leading figures in Warren’s circle balked at the outreach effort — Sanders and his aides, they said, had months to lay the groundwork for that kind of partnership, but only did so this week from a position of desperation. About a month ago, when it was clear that Warren had little chance to win, one such person said they put out feelers to Sanders’ operation in an attempt to start a running conversation. They showed little interest, the person said, in reciprocating.