Joe Biden shored up the Democrats' “blue wall,” — more sturdily in Michigan, more tenuously in Pennsylvania and Wisconsin — to rebuild the party's path back to the White House.

And while The Associated Press had called all three states and their combined 46 Electoral College votes for Biden, the Democrat's relatively narrow margins there reflect the nation’s continuing deep divisions more than a newly strengthened Democratic bulwark in the industrial north.

Trump had stunned the country four years ago by winning the three states that had been carried for decades by Democrats by a total of 77,000 votes. He did particularly well in rural areas and among non college-educated white voters, and his victory showed a fraying of the Democratic coalition as more working-class voters viewed their former party as dominated by coastal elites who considered their homes “flyover country.”

Biden, from the start, sought to reclaim at least some of those voters, making his appeal as a son of Scranton, Pennsylvania, who attended a state college, had known financial struggle, and could relate to their concerns.

“Joe Biden won these states because he and his campaign focused on how to win them individually,” said Amy Chapman, a senior adviser to Democrat Barack Obama’s campaigns in Michigan.

But to Sen. Roy Blunt, R-Mo., “the blue wall is at best a blue speed bump now," telling ABC's “This Week” on Sunday, “This is a competitive country.”

Biden's slender margins underscored that the Democrats have work to do if they want to solidify this cluster of states that have been integral to them winning presidential elections.

“It’s a mistake to ever have thought Wisconsin was a safely blue state,” said state Democratic Chairman Ben Wikler.

Four of the past six presidential elections were decided by less than a percentage point in Wisconsin. “Wisconsin will be a pivotal battleground for the foreseeable future," Wikler said. "We're on a knife’s edge.”

Indeed, the Trump campaign has asked for a recount of the state's vote. The Associated Press has called the state for Biden, who has a lead about 20,000 votes, roughly the same margin Trump carried the state by four years ago.

To reverse Clinton's losses in the “blue wall” states, Biden benefited from both strong suburban turnout and in the urban centers of Philadelphia, Detroit and Milwaukee. He was also able to shave Trump's winning margins in working-class, swing-voting regions.

“Our suburbs are just becoming more and more Democratic,” said former Pennsylvania Rep. Ryan Costello, a Republican and Trump critic. “Some of that is natural. But a big chunk of that is attributable to Donald Trump, who he is, and everything he does that is such a turnoff for suburban voters."

With nearly all the votes reported in Chester County, Costello's home, Biden was leading Trump by 17 percentage points, 10 better than Clinton's margin.

Biden had received roughly 150,000 more votes than Clinton did across Chester and Philadelphia's three other neighboring counties — Bucks, Delaware and Montgomery — and was winning about 60 percent of the suburban vote, better than Clinton.

Even in losing Republican-heavy Waukesha County, Wisconsin, Biden's suburban gains were part of his winning Wisconsin formula.

Biden reached nearly 39 percent in Waukesha County, the state's most populous Republican-heavy county. The last Democrat to carry it was Lyndon Johnson in the landslide of 1964.

What's more, Trump fell short of a 60 percent in the combined GOP suburban bloc of Waukesha, Ozaukee and Washington Counties, where even losing Republican Gov. Scott Walker in 2018 reached 65 percent.

“There’s little overstating the significance in the swing in these suburban counties,” said veteran Wisconsin Democratic campaign strategist Teresa Vilmain.

Unlike Clinton, who did not visit Wisconsin during the general election campaign in 2016, Biden visited Wisconsin three times, even as he strictly limited his in-person campaigning in many states during the coronavirus pandemic. Biden traveled to Michigan four times, but campaigned most in Pennsylvania, 14 times.

While Trump campaigned collectively to all three more often, Biden's campaign vastly outspent Trump's campaign in the three states, $148.7 million to $58.5 million, though other groups spent millions more on either side.

Biden also tailored his advertising and visits to state-specific dynamics, Michigan's Chapman noted. And while Democratic turnout in Detroit and Milwaukee rebounded from 2016, a boost to Biden, his messages to manufacturing-heavy regions near blue-collar Green Bay, Wisconsin, in September and Erie, Pennsylvania, in October, may have helped him trim Trump's edge in those swing-voting regions, where Clinton lost.

Trump carried Brown County, home to Green Bay, by a smaller percentage than he did in 2016, and lost Erie County in Pennsylvania, where he had won four years before but where the economy continues to struggle. Trump also lost Saginaw County, Michigan, a struggling former General Motors supply manufacturing county Obama carried before the president flipped.

“We'd heard so much about the Trump economy. But we're still a manufacturing economy and nearly stagnant in our growth,” Erie County Democratic Party Chairman Jim Wertz said. “The Trump economy has not translated into a groundswell of work and opportunity here in Erie County. Joe Biden had the right message for this part Pennsylvania.”

While aggressive Democratic organizing — the vast majority of it virtual during the pandemic — was also part of what helped push Biden just over the goal line, the win did not dramatically alter the political landscape in these states.

There were notably smaller changes.

Biden captured Sauk County, won by Obama and Trump. The rolling stretch north of Madison is reflective of the state, with Democratic-leaning suburban and exurban growth areas to the south and it's more lightly populated GOP-leaning agricultural north.

Biden also captured Door County, Wisconsin, where Trump had won after Obama.

A sign of Democratic growth appeared in Biden's carrying once GOP-heavy Kent County, Michigan, where newcomers in the medical field are diversifying its electorate. The western Michigan county is the home of the late former Republican President Gerald Ford and where Trump's Secretary of Education Betsy DeVos retains a permanent residence.

The results in Michigan were one area where Democrats could sense a reversal. Trump won the state by 10,704 votes in 2016. Biden's margin over Trump is about 150,000.

Overall, though, there were hardly the dramatic changes to the maps as in 2016, when Trump carried 21 Wisconsin counties won four years earlier by Obama and 11 in Michigan. Trump flipped only 3 Obama counties in Pennsylvania. Biden turned only four back to Democrats across the three states.

Likewise, Trump’s increased turnout in rural areas, where Democrats were dubious he could recreate the 2016 turnout, caught them by surprise.

However, with Trump presumably off the ballot, former GOP Rep. Jim Greenwood of Pennsylvania sees the state sliding back to a Democratic-leaning state, as Trump supporters recede, uninspired by more conventional politicians.

“I view Trump as a sort of a one-off,” said Greenwood, among the Republicans who campaigned and raised money for Biden. “Without Trump on the ballot, we’re kind of back to a more stable politics.”

But Republicans like Costello, though just as critical of Trump, noted GOP state legislative gains that might prompt Republicans to view Trump's style as the answer—a pitfall when so many suburban voters chose Republican statehouse candidates but Biden for president.

“I'm concerned that both parties are going to learn the wrong lesson," Costello said, “and that things will get worse before they get better.”