SLIPPERY ROCK, Pa. (AP) — President Donald Trump’s campaign has a bold theory for how he will win reelection: It can tap a universe of millions of supporters who did not vote for him in 2016 but will do so this time.

Supposedly, these voters are overlooked by polls that show Trump consistently trailing Democrat Joe Biden. They are mostly the white working class from factory towns, farms and mining communities that Trump has elevated to near-mythic status as the “forgotten Americans.”

They are disaffected and disconnected from conventional politics. Yet they flock to the president’s rallies, plaster their yards with signs and have been filling up voter registration rolls, the campaign insists.

This strategy will be tested in Pennsylvania, a critical state that Trump carried by only 44,292 votes out of 6.1 million cast in 2016. To hold on to Pennsylvania’s 20 electoral votes, the president needs to prove that a hidden groundswell of supporters exists — and will vote.

“Trump has to drive turnout,” said Terry Madonna, a professor at Franklin & Marshall College in Lancaster who has conducted polls in the state for almost three decades. “I don’t see any evidence that he’s expanded his base.”

The strategy is more difficult to execute given the stunning disruption wrought by the coronavirus pandemic, both in terms of a public health crisis and nationwide economic dislocation.

So his fate lay in large part in places like Butler County, an overwhelmingly white, conservative county north of Pittsburgh. There are nearly two Republicans for each registered Democrat. Most adults did not graduate from college. The economy rests on manufacturing and fracking, as well as from suburbs creeping in from the city.

Republican turnout in Butler County was an impressive 80% in 2016. But local Republicans say the goal is to push that number as high as 90% this year. And they’ve spent several months registering new Republicans, adding 9,043 of them this year alone, for a 12.8% increase. Trump’s campaign is trying to replicate those kinds of numbers in other rural and exurban counties in the state.

Al Lindsay, the 74-year-old trial lawyer and farmer who leads the Butler County Republicans, says that registration push has been made easy by frustrations over pandemic lockdowns and a growing belief that Democrats no longer understand people who are religious and rural. But given the shift to Democrats around Pittsburgh and Philadelphia, his pitch is simple: “Look, there’s an urgency here. We need you.”

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Republicans been operating three campaign offices in the county — a declaration of their intention to dominate. Slippery Rock Mayor Jondavid Longo pushed to open one of those offices in his town of 3,600. It sits opposite North Country Brewing, the town’s second-largest employer after Slippery Rock University, where Longo, a former Marine infantryman, attended college.

Trump “has given us an energy that says, don’t back down, stand up for what’s right,” said Longo, 30. “Open your mouth when you feel compelled to do so.”

Republicans like Longo focused on new registrants, but they’re also hunting for voters like Dane Patricelli, a 27-year-old construction worker who leans conservative but cast his ballot in 2016 for Libertarian Party candidate Gary Johnson.

Patricelli said Trump seemed like too much of a wild card in 2016. He wrestled for months with his decision this year, believing that Biden was a moderate even if the Democrats were drifting leftward. But he ultimately decided last week — after the last debate — that Trump had earned his vote.

“I do like Trump because he’s shaken things up and is not bought and paid for,” he said. “He’s sticking to his promises.”

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In Pennsylvania, Democrats still outnumber Republicans by more than 700,000 registered voters and there are another 1.3 million who are not associated with either party. And an Associated Press analysis of voting in key counties demonstrates the hurdles the GOP faces to overcome Democratic enthusiasm.

Butler County has 10,600 Republicans who were registered but did not vote in 2016. About 11% of them decided to cast a ballot in this year’s Republican primary, in which Trump ran unopposed, according to the analysis using data from L2, a political data firm. That’s a strong indicator that those voters are likely to vote again this year.

A similar pattern played out in 10 major Republican counties in Pennsylvania: Just over 10% of registered Republicans who sat out 2016 voted in the 2020 primary. That translates into nearly 14,000 voters.

The obstacle for Trump is that Democrats — they had a competitive presidential primary — have more voters and generated a better return rate. There are 258,000 Democrats who were registered but did not vote in Philadelphia and its surrounding counties in 2016. But during this year’s primary, more than 34,300 of them became voters and cast ballots. That’s more than double the gains in Republicans from the 10 leading Trump counties.

“For both campaigns, they’re seeing an acceleration of the trends we saw in 2016,” said Christopher Nicholas, a veteran Republican strategist. “Biden is doing better in the suburbs across the state. The Trump campaign is doing better in rural and exurban Pennsylvania.”

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Catherine Lalonde, 59, wasn’t even registered as a Democrat in 2016, but the trained nurse now leads the Butler County party. The Democrats’ office — it didn’t exist in 2016 — is a hive of candidates and voters picking up signs in the morning to replace those damaged or stolen during the night.

Trump signs might dominate, but frustrated Democrats feel a new urgency about expressing themselves.

“Other years, people tended to be a little more cautious about putting up signs because they’re in a place with a Republican majority,” Lalonde said. “But this year, they feel they have to do it.”

But in Butler County, for every eager Democratic voter like Lalonde there are more Republicans who are lining up to vote for Trump — and many believe that in this election, everything is at stake.

Bill Adams, 76, has long lamented the decline of U.S. manufacturing, having proudly opened up a suction-cup factory in Butler County after transitioning from work as an elementary school librarian. Adams is convinced the nation is at a precipice where Democrats would destroy businesses, if not personal freedom.

“I’ve never seen anything like it — we are where Venezuela was before the socialists took over,” he said. “That is the choice. It’s not what I think. It’s what history tells us.”

Trump will need many more like Adams if he is to win a second term.

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AP data reporter Angeliki Kastanis in Los Angeles and data reporter Pia Deshpande in Chicago contributed to this report.