It's been more than a week since President-elect Joe Biden's win in Pennsylvania returned the state to its decades-long pattern of picking a Democrat for the nation's highest office.
As voting totals continue to climb, it's becoming clearer how and why Biden won the battleground state.
Arguments can be made that a key to the Democratic challenger's victory was doing better in the red counties than Hillary Clinton did four years ago.
While that helped, driving down the margins in the red counties didn't help Biden as much as driving up the margins in the blue counties.
The Philadelphia suburbs made the biggest difference in the presidential election, according to Terry Madonna, pollster and political analyst at Franklin & Marshall College in Lancaster.
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Those suburbs are the four counties surrounding the city in the most heavily populated area of Pennsylvania: Bucks, Chester, Delaware and Montgomery counties.
Biden won those counties by about 300,000 votes, and he won Pennsylvania by more than 63,000 votes overall.
His victory comes four years after Clinton lost by about 44,000 votes when Donald Trump became the first Republican presidential nominee to win Pennsylvania since 1988.
Biden did better in the "collar counties" than Clinton, and it breaks down like this:
Bucks: Clinton won by 1%; Biden won by 4%
Chester: Clinton won by 10%; Biden won by 17%
Delaware: Clinton won by 22%; Biden won by 26%
Montgomery: Clinton won by 21%; Biden won by 26%
Trump made some gains in Philadelphia and closed the margin a little in the Democratic stronghold. Clinton won the city by 67% in 2016, and Biden won there by 63% this year.
State Rep. Kevin Boyle, a Democrat who represents northeast Philadelphia, told the Philadelphia Inquirer that Trump was able to stir support from Russian, Ukranian and Indian immigrants in his district.
However, the region overall remains blue, and that could help Democrats in the 2022 midterms - which include a U.S. Senate race and a gubernatorial contest in Pennsylvania - and in the 2024 presidential election.
"Hugely important," Madonna said. "It gives the Democrats a big advantage in statewide elections. The Republicans need to make inroads there."
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But despite a presidential win for Democrats, the Republicans won bigger majorities in the state House and Senate, and they flipped two state row offices: auditor general and treasurer.
"That's because the Republicans ran well in counties that Trump won," Madonna said. "It also looks like some Democrats down-ballot voted for them."
In other areas, Democrats did well.
In addition to the southeast corner, Biden improved in other blue counties:
Allegheny: Clinton won by 17%; Biden won by 20%
Centre: Clinton won by 2%; Biden won by 5%
Dauphin: Clinton won by 3%; Biden won by 8%
Biden also narrowly flipped back Erie and Northampton counties, which Trump won four years ago and former President Barack Obama won in 2012 and 2008.
Biden made modest gains in red counties, including Luzerne, Washington and Westmoreland. He made bigger progress in the most populated red counties in southcentral Pennsylvania:
Cumberland: Trump won by 18% in 2016; Trump won by 11% in 2020
Lancaster: Trump won by 19% in 2016; Trump won by 16% in 2020
York: Trump won by 29% in 2016; Trump won by 25% in 2020
"Midstate counties are counties to watch, especially Dauphin and Cumberland," said Jesse White, a political strategist at Perpetual Fortitude, a Democratic consulting and digital management firm.
In years to come, White sees Cumberland County becoming more of a swing county because of the evolving demographics of the county. The county is gaining college-educated voters and suburban women, who voted in favor of Democrats this year and in the 2018 midterms.
"Even when I look at off-year elections, I see Democrats closing the gap with Republicans," White said. "The right candidate could flip Cumberland County blue."
Biden won votes from Republicans
This year, Biden was the candidate that attracted votes from Republicans.
That's according to Tom McGarrigle, chairman of the Delaware County Republican Party, who has worked Election Day polls for 25 years.
He said he has never seen a turnout like he did on Nov. 3 and knew some of those voters were Republicans who waited in line to vote against Trump - mainly because of the president's handling of the coronavirus.
Trump is suing to overturn the results in the state and in other battlegrounds.
"People were dissatisfied," McGarrigle said. "Especially with the spike, he wouldn't wear a mask and then he got it, and then with this spike coming back around."
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There are other Republicans, however, who say the race isn't final.
"I understand there's not going to be a recount in Pennsylvania, but why would anyone stand in the way of that?" said Jeffrey Lord, a political analyst from Camp Hill who served as an associate political director in the Reagan White House.
"Trump voters want to feel confident in the vote count. And wouldn't Biden want everyone to know he won fair and square?"
The Associated Press contributed to this report.
Candy Woodall is a reporter for the USA Today Network. Follow her on Twitter at @candynotcandace.
This article originally appeared on York Daily Record: Election 2020: The Pennsylvania counties that helped Joe Biden win