Amid rapidly changing political head winds, Sen. Bernie Sanders (I-Vt.) on Thursday abruptly scrapped a campaign event scheduled for Friday at a civil rights museum in Jackson, Miss.

He will instead spend much of the weekend in Michigan, a shift that serves as a tacit admission of the seemingly insurmountable deficit he faces in his support among black voters in the Deep South against Joe Biden, who has reemerged as his chief — and now sole — major rival for the Democratic nomination.

The change reflects an increased urgency to win Michigan, a crucial test for the senator from Vermont. But it was also prompted by Sanders’s weak standing in Mississippi, according to a person with knowledge of the situation, who spoke on the condition of anonymity to speak candidly about strategy.

It’s a strategy similar to the one Sanders deployed in 2016, leaving Southern states to Hillary Clinton while shoring up support in the industrial Midwest. That gamble scored him narrow victories in states such as Michigan, which he won thanks to support from white voters — black voters in the state went 68 percent for Clinton and 28 percent for Sanders, according to exit polls.

But he lost handily to Clinton in places like Mississippi, where she beat him by 66 percent and amassed delegates at a faster clip.

This time, Sanders faces an added challenge in the Deep South. Biden has deep ties within the African American community, in part because he served as vice president to Barack Obama, the first black president.

 Biden has also spent decades cultivating relationships with prominent black leaders, who have lined up to endorse him.

Days before the South Carolina primary, he received a crucial endorsement from Rep. James E. Clyburn (D-S.C.). Biden went on to win South Carolina by nearly 30 points. His victory there — fueled by support from black voters — revitalized a campaign that had seemed less viable by the day after lackluster support in the Iowa and New Hampshire contests.

Derrick Johnson, the president of the NAACP, said Biden “approached the campaign from our vantage point,” and praised the former vice president for reaching out to a wide variety of local and national leaders.

Johnson said he has not seen the same level of engagement from the Sanders campaign, which has focused on turning out a new coalition of voters rather than reliable — and older — voters who make up the black Democratic base.

On Super Tuesday, which included a diverse cadre of states in the South and Southwest, Biden claimed broad support among African American voters, of which nearly 6 in 10 supported him, while 17 percent voted for Sanders. Voters who say race relations are the most important issue guiding their decision broke for Biden by 26 percent.

Meanwhile, Sanders’s Medicare-for-all pitch, a cornerstone of his campaign, appeared to be significantly polarizing. Of the voters who said health care was their top issue, 40 percent voted for Biden, vs. 28 percent who voted for Sanders.

Sanders has also faced criticism for saying after his Super Tuesday losses that Biden was being bolstered by the “establishment.” Anti-Sanders voters have seized on those comments to point out the ways in which Sanders sometimes undercuts his own message with black Democratic voters.

Theodore R. Johnson, a researcher of black political behavior and a senior fellow at the Brennan Center for Justice, said he found Sanders’s comments about Biden’s coalition to be deeply frustrating.

“Black voters are not and have never been ‘the establishment.’ Black voters in the South have grown up in cultures and societies that oppress them just for speaking up, and have adopted a type of politics that have allowed them to survive and thrive in those conditions,” he said. “Attacking them for behaving the way they did politically is bad form. It’s disingenuous and many people in the black community are saying it’s kind of racist.”

Johnson stressed that black voters are not monolithic — their political preferences vary by region, age, income level and other variables, like any other group. In the Midwest and in California, “there might be something about those voters making them more willing to take a chance on the progressive candidate.”

But in deep Southern states like South Carolina, or proximate states like Virginia, where black voters tend to be older and more religious, there is an underlying skepticism of political unknowns, especially those who make big promises, he said.

“For groups that are mostly risk-averse in how they vote traditionally, it’s better to be known and trusted than to show up with a long list of policies that you promise to pass once you’re in office,” Johnson said.

He added that, with the field narrowing to just two candidates, Biden’s strength among black voters was likely to consolidate and grow.

This isn’t the first time this cycle Sanders has skipped an event in the South. Days before Super Tuesday, he skipped a “Bloody Sunday” anniversary event in Selma, Ala., traveling to California instead.

But Sanders’s pivot to Michigan also reflects concern among aides that he may already be trailing Biden there. They say Sanders will try to draw a sharper contest with Biden in the coming days on issues like trade and Social Security.

When he spoke to reporters after Super Tuesday, he reiterated a focus on the Midwest as the region where he would hold Biden accountable for his record.

“Michigan, Wisconsin, Indiana, the Midwest in general, Minnesota, have been very hard hit by disastrous trade agreements. And Joe is going to have to explain to people, the union leaders why he supported disastrous trade agreements ... that resulted in a race to the bottom,” Sanders said.

But as Sanders goes all in on Michigan, Biden is campaigning hard there, too, sending surrogates like . Amy Klobuchar of Minnesota and unfurling high-profile endorsements, like the state’s governor, Gretchen Whitmer.

“Now let’s go to Michigan, Bernie,” Biden said on NBC’s Today Show. “Let’s see if that’s true. I’m the guy that helped bail out the automobile industry. What did you do, old buddy?”

On Wednesday, Sanders downplayed how vital a Michigan win was to his path to the nomination, but said it’s a state he hopes to win.

“Look, we are going in there with the full expectation and the hope that we will win,” Sander said. “Michigan is obviously a very important state. It’s a state I feel very comfortable in.”

Sean Sullivan and Holly Bailey contributed reporting.