Joe Biden's decisive victory in Michigan’s presidential primary offers what some Democrats hope will be the road map for success in November — a high turnout powered by a coalition that extends into territory Donald Trump won in 2016.

Biden beat Vermont Sen. Bernie Sanders last Tuesday among key demographics — African American, suburban and working-class voters — that the Democratic Party failed to coalesce nearly four years ago. Michigan saw a record turnout of nearly 1.6 million voters in the primary — a jump of nearly 30% over 2016.

But the contest also flashed a warning sign about African American support: While suburban voting soared, it slouched in Detroit, a majority black city where slipping turnout contributed to Democrats' bruising 10,000-vote loss in 2016.

That suburban-urban divide jumped out as Democrats in Michigan, the first swing state to vote in the Democratic primary, searched for lessons to apply to the looming battle ahead against Trump. While many state Democrats celebrated their big turnout, some urged caution that enthusiasm among black voters, particularly young black voters, should not be overlooked.

A strong showing across the state may sound impressive, but in November flagging interest in Democratic strongholds may matter more, said University of Michigan political science professor Vincent Hutchings.

“It’s a nice news story to talk about winning every county in Michigan, but it’s certainly not going to happen in the general election," he said. “But he (the eventual presidential nominee) doesn’t have to win all of the counties or even most of them because most of the population is in the Detroit metro area, which is obviously dominated by African Americans. In terms of winning the general in Michigan, it’s going to be largely about black voters.”

Tuesday's turnout “explosion," as state party officials called it, revealed Democrats' growing dependence on these suburban areas, which are rapidly diversifying and trending blue in the Trump era.

In the three counties of metro Detroit — Wayne, Macomb and Oakland — Biden found some 78,000 more votes than Hillary Clinton when she lost to Sanders in Michigan in 2016.

Together the three counties delivered 150,000 more Democratic votes compared with four years ago and a stunning 400,000 more than in the 2008 primary fight between Clinton and Barack Obama. Democratic voting in Macomb, a Trump county known as home to the working-class party switchers once dubbed Reagan Democrats, was up more than 30%.

Voter turnout in Detroit, meanwhile, decreased about 11% from about 127,000 in 2016 to roughly 113,000, according to unofficial results.

The drop may be partially explained by a decrease in registered voters in the city, which dropped from more than 503,400 in 2016 to 482,621 this year, as population has declined.

But some elected officials believe the party needs to do more to build enthusiasm and interest among Detroit voters.

“I think that one mistake that's often made is not enough engagement of our young people,” said Michigan state Rep. Sherry Gay-Dagnogo, who represents northwest Detroit. “You have to go where they are and understand the plight that people are dealing with. I'm hopeful that whoever the candidate is, that they would acknowledge that many people here are struggling and they're hurting.”

In primary contests so far, Biden has enjoyed strong support among black voters, a group that essentially rescued his campaign in South Carolina and helped set him on a path toward the nomination in only a matter of weeks. That's according to AP VoteCast surveys of thousands of Democratic primary voters in many of the states that have already voted.

In Michigan, where black voters made up about one-fifth of the primary electorate on Tuesday, 59% of black voters supported the former vice president, while 32% went for Sanders. That's a notably lower share than Biden has received in some Southern states, where blacks make up a majority of Democratic voters.

But Biden undoubtedly has some ground to make up with young voters of all races, the core of Sanders' support.

Nicole Thirkield said she voted for Sanders largely because of his policy for student loan debt forgiveness.

“I'm hoping that whoever is in office is actually trying to fight for us and push for that,” Thirkield, a 30-year-old Oakland County resident, said.

Oakland County resident Alicia Jones struggled with whom to vote for on Tuesday. Jones, 60, does community work in Detroit and said the candidates need to speak directly to issues facing urban cities.

“There’s no clear urban African American agenda and none of them had that,” Jones said, adding that she considered not voting for the first time in her life. Jones declined to say how she voted, though she said she plans to vote in November begrudgingly. “It was difficult for me to vote and to vote Democratic. Who’s going to help us? Who’s going to eliminate the disparities and address the real issues? It just wasn’t clear for me.”

Longtime Detroit political consultant Greg Bowens said the eventual nominee also needs to create a ground game that reaches across urban and suburban black voters.

“Some of that gets lost,” Bowens said. “The challenges of being an African American don't disappear because you move. What it does for November is it forces us as a party to rethink the way that we approach elections. If you're working to turn people out in Detroit, it's assumed that they're mostly black. But when you put those efforts in the suburban communities, you don't have that same kind of effort that you would in the city.”

Howard University political science department chair Ravi Perry said Michigan's turnout increase across the state could point to voters uniting in hopes of removing Trump from office.

__

Associated Press writer Hannah Fingerhut contributed from Washington. Kat Stafford is a member of The Associated Press’ Race and Ethnicity team. Follow her on Twitter at https://twitter.com/kat__stafford.

___

Catch up on the 2020 election campaign with AP experts on our weekly politics podcast, “Ground Game.”