It is clear why Mr. Sanders is scrambling — the Super Tuesday results carried ominous signs for his candidacy. In next-door Minnesota, for example, Mr. Biden did not visit once but still defeated Mr. Sanders 44-32 among white voters without a college degree, according to exit polls.
Representative Dan Kildee, a longtime Michigan Democrat who has not endorsed a candidate in the presidential race, said Mr. Sanders was in a far weaker position going into Tuesday than he was four years ago. Voters then wanted to slow Mrs. Clinton’s front-running campaign and did not feel the level of Trump-inspired alarm that they do now.
“Those factors conspired against Hillary much to the benefit of Bernie,” Mr. Kildee said. “The feeling that she was inevitable, and his supporters were much more animated. And there was just, among some, a lack of enthusiasm for her campaign.”
Now, Mr. Kildee said, Mr. Biden is experiencing a surge of enthusiasm because of “the absolute commitment to beat Donald Trump.”
Brandon Dillon, a former chairman of the Michigan Democratic Party, said, “I know people personally who voted for Bernie because they wanted to send a message to Hillary.”
Now, Mr. Dillon said, Mr. Sanders isn’t “a novelty anymore.”
“People just want to want to win because we know who our opponent is and what he can do if he gets another four years,” he continued.
Some of the more Clinton-friendly precincts from 2016 may be even more hospitable to Mr. Biden now that Michael R. Bloomberg, the former mayor of New York, is out of the presidential race. Polls taken while Mr. Bloomberg was still running showed Mr. Biden leading but with the former mayor of New York, who poured tens of millions of dollars into the state, also receiving some votes.