DETROIT — Four years ago, Senator Bernie Sanders scored an upset win over Hillary Clinton in the Michigan Democratic primary, reviving his insurgent candidacy one week after his political prospects dimmed because of Super Tuesday losses.
Now Mr. Sanders, of Vermont, finds himself once again urgently in need of a bounce-back victory in Michigan’s presidential primary after another disappointing Super Tuesday, this time against former Vice President Joseph R. Biden Jr.
Mr. Sanders has shaken up his schedule to hold three days of events and rallies in Michigan. He has intensified his attacks on Mr. Biden over trade, a major issue in the state; in remarks in Dearborn on Saturday, he recalled joining picket lines to protest “disastrous” trade deals. And his campaign arranged an event in Flint on Saturday night for the explicit purpose of Mr. Sanders making his case to black voters, who have largely favored Mr. Biden so far. The Flint event mostly drew white voters, though, and Mr. Sanders mostly reiterated his stump speech.
As Mr. Biden now attempts to leverage his Super Tuesday success and build momentum, Mr. Sanders may face even longer odds in Michigan than he did in 2016. The state that Mr. Sanders last week called “very, very important” suddenly looks forbidding for him.
Mr. Biden, despite having a thin operation in Michigan, appears likely to do well with black Democrats and college-educated white voters, two groups that handed him decisive margins in Virginia, North Carolina and several other states on Super Tuesday. And the exit polling and voting trends in some of those states indicate that Mr. Sanders has declined in strength with working-class white voters, who, uneasy with Mrs. Clinton in 2016, delivered him landslide wins across much of central and northern Michigan that year.
Michigan, with its 125 delegates, is the most populous state to vote on Tuesday, and it is the first of the big Midwestern battlegrounds to cast ballots — a general election trophy that President Trump painfully pulled from the Democratic column in 2016 with a narrow win. But Michigan also could amount to a bellwether for the rest of the Democratic primary race this spring.
With Mr. Biden appearing strong in the South and Mr. Sanders winning in the West, the industrial Midwest could effectively determine the nomination. And if Mr. Sanders can’t win in Michigan, he may struggle when Ohio and Illinois vote on March 17 and Wisconsin on April 7, while also undercutting his claims about expanding the electorate in some of the most pivotal general election swing states.
“Michigan is an important state to do well in because the issues facing residents here are issues we see across the country, so a strong message and showing here will be extremely helpful for the nomination,” said Representative Rashida Tlaib, one of Mr. Sanders’s most prominent supporters in the state.
Recognizing the stakes here, Mr. Sanders is assailing Mr. Biden for his support of what he called “disastrous trade agreements like Nafta.” And his campaign is airing a commercial in the manufacturing-heavy state that features a former autoworker highlighting the former vice president’s lack of regret for supporting the pact while pointing out that Mr. Sanders has opposed free trade deals.
As he addressed supporters in Dearborn, Mr. Sanders devoted about a third of his stump speech to attacking Mr. Biden, lashing him not only on trade but also over entitlement programs, support for the war in Iraq and a willingness to take donations from wealthy donors.
“Our campaign and our administration is about representing the working families in the country,” Mr. Sanders said.
Abdul El-Sayed, a Sanders supporter who ran for governor in 2018, said he believed that Michigan Democrats would see clear distinctions between the two candidates.
“Free trade helped decimate those manufacturing jobs — Bernie has always been against it, Biden has been for it,” he said.
But recent election trends in Michigan are not encouraging for Mr. Sanders. In 2018, Michigan Democrats rallied behind a number of moderates — most notably Gretchen Whitmer in the governor’s race, and Haley Stevens and Elissa Slotkin in congressional races — and ended up winning Republican-held seats and loosening the G.O.P.’s grip on the state.
Mr. El-Sayed, who ran against Ms. Whitmer for governor on progressive issues like “Medicare for all,” enjoyed Mr. Sanders’s support and a flood of news media attention in 2018, but did not capture a single county in that primary. Ms. Whitmer, a former Democratic leader of the State Senate whose most memorable vow was to “fix the damn roads,” beat him by nearly 22 points.
While the race was somewhat competitive in Detroit and around Ann Arbor, home of the University of Michigan, Ms. Whitmer ran up enormous margins across much of rural Michigan.
“The Whitmer primary victory over El-Sayed paints a clear road map for Biden over Bernie,” said Eric Goldman, who ran Ms. Whitmer’s campaign. “Biden will excel where Whitmer won big plus he’ll run up the score with black voters.”
Mr. Sanders’s candidacy may in fact hinge on whether he’s able to perform better with African-Americans in the Midwest than he has in the South — and if he can replicate his strength with working-class white voters who abandoned Mrs. Clinton in the primary and general election. Mr. Biden’s supporters, in turn, believe that he is better positioned than Mrs. Clinton was, including with union members who like the former vice president and don’t want their health insurance to change under a Medicare for all system.
“The connection with the workers here is at a completely different level,” said former Mayor Mike Duggan of Detroit, a Biden supporter, noting the former vice president’s support for the auto industry during the Great Recession. “We have a candidate who I think will bring the traditional Democratic coalition back together.”
Also lifting Mr. Biden in Michigan is some of what helped him going into the primary last Tuesday in Virginia, where many of the state’s leading Democrats endorsed him in the run-up to the balloting. Ms. Whitmer, Ms. Slotkin and Ms. Stevens all threw their support behind Mr. Biden this past week.
In an acknowledgment that his campaign would be grievously wounded if he did not rebound in Michigan, Mr. Sanders canceled an event scheduled for Mississippi, which also votes Tuesday, to spend more time here. And he has abruptly started to attack Mr. Biden on abortion rights, not an issue the democratic socialist typically uses against his intraparty rivals.
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.
Yet now that Mr. Bloomberg has withdrawn and endorsed Mr. Biden, some of his supporters appear poised to migrate to the former vice president; a Detroit News survey taken before Super Tuesday found 49 percent of Mr. Bloomberg’s supporters indicating that Mr. Biden was their second choice, while just 18 percent said Mr. Sanders was their second choice.
These Bloomberg-to-Biden voters could prove especially crucial in the Detroit area, which was where Mrs. Clinton ran the strongest. In suburban Oakland County, for example, Mrs. Clinton won by about five points in 2016. But after Mr. Biden’s commanding margins in similar upscale communities on Super Tuesday, many Michigan Democrats expect him to win by far more there.
“Those women are voting for Joe Biden against Bernie Sanders and they’ll vote for him again against Donald Trump,” State Senator Adam Hollier said of the suburban women who helped power the Democrats in the midterms, and who surged to the polls last Tuesday.
Just as worrisome for Mr. Sanders, the same Detroit News poll had Mr. Biden winning 40 percent of black voters while Mr. Sanders was taking just 16 percent.
Mr. Hollier, who initially supported former Mayor Pete Buttigieg of South Bend, Ind., represents a legislative district in and around Detroit that includes a number of working-class black neighborhoods as well as some of the most affluent enclaves in the state. He said, “everybody in my circle is coalescing around Joe Biden.”
At first, he said, black and white voters alike were “looking for President Obama — but instead we went with the one we’ve always felt comfortable with.”
Lisa Lerer contributed reporting from Dearborn, Mich.