“Our feeling was that Senator Sanders should have said something earlier and should have been stronger about it,” said Bethany Khan, a political strategist for the union.
And then there was Cuba: In February, Democratic officials in Florida reached out to propose convening some conversations between Mr. Sanders and Latino leaders in South Florida, many of whom were nervous about his rhetoric on socialism and revolution. The Sanders campaign showed tentative interest, people familiar with the conversations said.
Then, the day after the Nevada caucuses, CBS aired a “60 Minutes” interview in which Mr. Sanders stood by his past praise for certain policies of Fidel Castro’s government. Democrats across Florida, including prominent members of Congress, erupted in dismay.
Mr. Sanders stood his ground, including in a televised debate. And he made no attempt at private damage control: None of the lawmakers who rebuked him in public heard from Mr. Sanders or his senior aides.
His campaign eventually dispatched emissaries, including the actress and activist Cynthia Nixon, to meet quietly with Latino groups in Orlando after Super Tuesday, but they could not assure local Democrats that Mr. Sanders would change course before Florida’s March 17 primary.
“It may be authentic to Bernie, but it does not work in Florida,” said Alex Barrio, a Democratic activist in Florida who attended the meeting. “It’s conceding Florida in a monumental way.”
By the time Florida voted, however, the race was all but over.
Mr. Sanders’s campaign, like much of the political world, had not anticipated Mr. Biden’s roaring comeback after South Carolina’s Feb. 29 primary. Indeed, until then, Mr. Sanders’s campaign was expecting to win seven or eight of the 14 states voting on Super Tuesday and seize a solid delegate lead over the rest of the Democratic field.