In a critical state that Trump won by only 44,000 votes in 2016, Tuesday’s results demonstrate that maintaining that narrow advantage will be an enormous challenge for the president next year.

“The anti-Trump sentiment in the suburbs hasn’t dissipated at all,” said Ryan Costello, a former Republican congressman from Chester County. “Democrats have won counties they never, ever, ever won. The trend from red to blue has accelerated in the last few years, and there’s only one reason for that."

The risk for 2020, he said, is “there is not a way to win Pennsylvania, Wisconsin and Michigan without holding your deficits down in the suburbs.”

The election wasn’t all good news for Democrats. While liberal activists were toasting historic victories in populous southeastern Pennsylvania on Tuesday night, Republicans were simultaneously raising a glass for first-ever wins in the western part of the state.

The GOP took the majority in Washington County’s local government for the first time this century. It also scored a rare triumph on the Johnstown City Council and flipped county commissions in Greene, Armstrong and Westmoreland counties in the west — where Trump’s strength runs deep.

“This affirms that Trump will be formidable in 2020,” said Democratic Lt. Gov. John Fetterman, who was formerly mayor of a hardscrabble steel town in western Pennsylvania. “It’s wonderful that we have Delaware County for the first time since the Civil War, but Washington County just went red for the first time in over 100 years.”

A political realignment has been underway for years in Pennsylvania: The GOP has bled college-educated voters in the southeastern suburbs at the same time that working-class white people have abandoned Democrats in the west.

Despite losing the Philly suburbs in 2016, Trump became the first Republican presidential candidate to carry the state since 1988 by scoring big wins in rural areas and onetime Democratic strongholds in western Pennsylvania. Republicans and western Democrats believe that the 2019 election showed that Trump could pull that off again.

“It’s Trump country, Trump country, unbelievable Trump country,” said former state GOP leader Rob Gleason in explaining the Republican victories in the region.

“It continues to be a tale of two Pennsylvanias,” he added. “I think the president still has a very good shot of winning Pennsylvania because the supporters in the counties that voted for him in 2016 have pretty much dug in their heels.”

Suburban Democrats acknowledge that Trump remains powerful in the western part of the state, but they believe their victories in recent years in Philly’s collar counties illustrate that they can post even bigger Democratic margins in 2020. In addition to their historic finish in Delaware County this year, Democrats also won back the Bucks County Board of Commissioners for the first time since the 1980s and swept the county commissioner races in Chester County.

“That’s the only way for the Democrats to change the results of those 44,000 votes,” said Dave Delloso, a Teamsters leader who in 2018 flipped a state House seat in Delaware County for the first time in 40 years. “You leave metropolitan Philadelphia 1 million, 1.2 million votes ahead.”

From Cambria in the west to Bucks County in the east, Democrats and Republicans both saw the 2019 election as a way to jump-start organizing for the presidential race.

In Philly, the Working Families Party made history by winning one of the two seats on the city council that is set aside for candidates who are not part of the majority party — in other words, the Democratic Party. Republicans had held those set-aside seats for decades.

Given that it required an extensive educational program to persuade city voters that they could support WFP candidate Kendra Brooks without hurting Democrats — voters can only cast a ballot for five candidates running for seven total seats — her victory indicates that there is a massive number of highly engaged progressives in the city.

“Kendra won with 55,000 votes, and Trump won the entire state of Pennsylvania with 44,000 votes. So the work we have to do tomorrow is consolidate that coalition,” said Maurice Mitchell, national director for the Working Families Party, who added that the victory represents “hundreds and hundreds” of volunteers in 2020, including many of whom are new to the political process. “In a non-delusional way, the Working Families Party coalition in Pennsylvania could rob Trump of his victory in the country and save the world.”

Though Philadelphia is a bright-blue city, Republicans successfully worked in 2016 to narrow their losses in the city compared to the 2012 presidential election — and they need to replicate that again next year.

"It allowed Trump to win because we cut" votes in Philly , said Gleason, the former state GOP leader. “Losing to the WFP falls squarely on the city chairman’s head — and he should resign.”

But Brooks’ victory was also a blow for the city's Democratic establishment, which had threatened to expel party officials and who backed the Working Families Party. What, former Rep. Costello wondered, will happen if Democrats nominate a moderate candidate such as Joe Biden who simultaneously comforts suburbanites but doesn’t appeal to the left?: “What does that do to really progressive voters?”

Despite some national polls showing Trump behind his likely Democratic opponents by double digits, Tuesday’s election underscored for many top Democrats and Republicans in Pennsylvania that 2020 will likely be another fight at the margins.

“What happened is that the people of Delaware County are understanding more and more how dangerous the Trump agenda is for their lives,” said Colleen Guiney, the chairwoman of the Delaware County Democratic Party. But, she added, “I take no election for granted.”