BURLINGTON, Vt. — Senator Bernie Sanders has canceled a planned rally in Jackson, Miss., and will instead travel to Michigan on Friday, a striking indication that his presidential campaign is shifting its focus to the Midwest and largely ceding another Southern state to former Vice President Joseph R. Biden Jr., according to people familiar with the plans.
After holding a rally in Phoenix on Thursday night, Mr. Sanders had been scheduled to travel to Jackson on Friday for a rally focused on racial justice.
The change in plans suggests that Mr. Sanders will not challenge Mr. Biden for the support of black voters in the South — a vital base in the Democratic Party — and is instead going all-in on the Midwest as he tries to compete with Mr. Biden for working-class voters there. Black voters in the South have overwhelmingly backed Mr. Biden to this point, and on Super Tuesday their support lifted him in states like Alabama, North Carolina and Virginia.
In Alabama, Mr. Sanders won only 9 percent of black voters, compared with 72 percent for Mr. Biden, according to exit polls. Mr. Biden outperformed Mr. Sanders among black voters in Virginia by more than 50 points, and by 40 points or more in Texas and North Carolina. In several states, Mr. Sanders came in third among black voters, behind not only Mr. Biden but also Michael R. Bloomberg.
The dramatic shift in his schedule was also an acknowledgment that he had not improved his standing among black voters in the South four years after his first run for president. In 2016, he faced criticism for his inability to organize support from black voters, a weakness that contributed to his loss to Hillary Clinton in the Democratic primary.
Mr. Sanders indicated he planned to focus on the Midwest during a hurried news conference with reporters on Wednesday. Asked if he had to win next Tuesday in Michigan — a primary he won in 2016 — Mr. Sanders suggested he did.
“We are going in there with a full expectation and the hope that we will win,” he said. “Michigan is obviously an enormously important state. It’s a state I feel very comfortable in.”
He also underscored the importance of other Midwestern states, including Wisconsin and Indiana. President Trump won both of those and Michigan in the 2016 general election; former President Barack Obama won all three in 2008.
Sanders aides are confident that Mr. Sanders lines up favorably against Mr. Biden in the industrial Midwest, and they have already laid out plans to highlight Mr. Biden’s record on trade, which includes voting for the North American Free Trade Agreement. While many blue-collar voters say they feel a connection to Mr. Biden, many have also grown increasingly suspicious of free trade in the Trump era.
In an interview, Faiz Shakir, the campaign manager for Mr. Sanders, said the campaign was considering running an ad in Midwestern states like Michigan and Ohio that will emphasize Mr. Biden’s record on trade, and Mr. Sanders has already added blistering remarks about Mr. Biden into his stump speech.
A crucial part of Mr. Sanders’s argument has been the idea that he is the most electable candidate, able to defeat Mr. Trump in a general election by appealing to the same white working-class voters who helped hand Mr. Trump his victory in 2016. But among aides and advisers, there has been a growing recognition that his claim hinges on his ability to demonstrate this strength in Midwestern states during the primary.
Mr. Sanders’s disappointing performance on Super Tuesday — he won only four states to Mr. Biden’s 10 — has only increased the sense of urgency inside his campaign.
During his news conference on Wednesday, Mr. Sanders said he was “disappointed” in the results on Tuesday. And in an extraordinary concession, he admitted that his campaign had not managed to generate the soaring turnout among young people that he had banked on to secure the nomination.
While Mr. Sanders has managed to draw support in high numbers among other demographic groups, including Latino voters, his deficit with black voters in the South was central to his losses on Super Tuesday.
Rather than cite his own shortcomings, however, Mr. Sanders has pointed to his opponents’ strong connections with African-American voters. In an interview on Wednesday night with Rachel Maddow of MSNBC, he suggested that Mr. Biden was benefiting from his relationship with Mr. Obama — and used a parallel argument to explain his deficit in 2016 as well.
“We’re running against somebody who has touted his relationship with Barack Obama for eight years,” Mr. Sanders said. “Barack Obama is enormously popular in this country in general and the African-American community. Running against Hillary Clinton, Bill Clinton was enormously popular.”
“It’s not that I’m not popular,” he added. “Biden is running with his ties to Obama and that’s working well.”
He also said he was generally doing well among voters of color, including Latinos, and with younger black voters.