WILKES-BARRE, Pa. — If there was one state where Donald Trump’s message was supposed to flip a reliable Democratic state, Pennsylvania was it.

With its 20 electoral votes and its considerable number of blue-collar workers and mining families, the state was seen as ripe for Trump’s promise to boost coal and natural gas, and bring back American jobs from overseas.

Instead, the “Keystone State” could spell big trouble unless Trump can quickly reverse the polls that show him steadily losing ground to Democrat Hillary Clinton since late September.

“You can’t overstate how badly he needs Pennsylvania,” said Terry Madonna, a political scientist and poll director at Franklin & Marshall College in Lancaster, Pa. “You can’t imagine Trump losing the election if he wins our state. For Hillary, it’s the firewall. If she wins here, it will put huge pressure on him to win all the other [swing] states.”

Pennsylvania is considered one of handful of essential states in the 2016 presidential race, along with Florida, Ohio, North Carolina and Nevada. Next to Florida, it’s considered the state most likely to be the “tipping point” for the election, according to the FiveThirtyEight blog, which, among other things, analyzes polls.

The race here has, by and large, moved stride for stride with the national polls. After Clinton built a lead in July, Trump closed to within less than 2 percentage points (on average) in late September. Earlier this month, Trump had fallen 6 points behind.

advertisement | advertise on newsday

Perhaps most revealing: polls show Clinton with a huge lead in four suburban counties surrounding Philadelphia that were once considered solidly Republican. That area is “a place where presidents are made or not,” Marist College pollster Lee Miringoff said.

Trump’s debate performances, a video that showed him talking about groping women, subsequent allegations about similar behaviors, and a falling out with elected Republicans have dampened support for him.

Further, Democrats have made an all-out push here (especially with women and college-age voters) with the Clinton team making numerous campaign stops and organizing voter registration efforts.

“I haven’t ever seen this many female students wanting to be engaged [in the election] and talking about being engaged,” said Temple University political scientist Robin Kolodny. She added that “unions are alive and well in [Philadelphia] and they are mobilized.”

Conversely, Republicans are “scared their mobilization efforts won’t work,” she said.

“Trump never developed a ground-game organization” in Pennsylvania, she said, referred to volunteers and field representatives that boost get-out-the-vote efforts. “And it’s not going to materialize in the final two weeks.”

When it comes to figuring out Pennsylvania’s electorate, it’s important to note that Philadelphia and the southeastern part of the state (areas better for Democrats) have grown, but the southwest part has lost population. That’s likely another factor for Clinton’s lead in the polls.

This is a state that hasn’t been carried by a Republican since the 1980s, though the GOP has been gradually improving its standing in the last few election cycles. Trump’s promise to boost coal and natural-gas energy production resonated in rural counties and communities, such as Wilkes-Barre, where anthracite coal was once king. Political-action committees backing Trump began spending big money here on TV ads.

Without a field team as robust as the Democrats, Trump has been relying on big rallies at indoor arenas and television coverage of those to boost momentum. To be sure, the Republican has been generating large crowds.

Thousands were lined up outside a hockey arena here, one day after the second debate between the candidates — the one dominated by the “groping” video. Supporters said they were convinced Trump would win here — just look at the crowds.

advertisement | advertise on newsday

“I’ve never seen enthusiasm like this,” said Michael Ayers, 45, who drove three hours from his home in South River, N.J., to “experience the movement.” He said he favored Trump on the issues of national security, taxes and jobs.

Carol Mead, from nearby Gibson, Pa., said she began the campaign year supporting Sen. Bernie Sanders of Vermont, who challenged Clinton for the Democrat nomination. She liked Sanders’ message about the “rigged economy” working only for those at the top of the economic pile. But when Sanders lost and endorsed Clinton, Mead said Trump became her choice.

“He’s a businessman — he’s coming from where a majority of Americans are coming from,” Mead said. “We are not deplorables. We are entrepreneurs. We are hardworking.”

The “deplorables” mention was a reference to Clinton saying that half of Trump’s supporters were a “basket of deplorables,” meaning people who are racist, sexist, homophobic or xenophobic. Clinton since has apologized.

Onstage at a recent rally here, Trump vowed he would win this key state and said polls that showed him behind here weren’t right because his advisers tell him that “everyone in Pennsylvania is for Trump.”

advertisement | advertise on newsday

Trump has been making such claims at stops in other states. Though a “hidden vote” for Trump can’t be ruled out, Madonna of Franklin & Marshall said pollsters would typically be tipped off to that by people refusing to answer survey questions. That hasn’t happened.

“Trump will do well in rural counties and places were coal, steel and iron were king,” Madonna said. But, as of now, there aren’t enough votes there to offset Clinton’s likely advantage in Pittsburgh, Philadelphia and their surrounding counties.

“What he hopes to get is a larger turnout than Romney. They’ve got to get their turnout up about 10 percent” above 2012, Madonna said, referring to then-GOP candidate Mitt Romney. “That’s what he’s pinning his hopes on, to be honest with you. I just don’t know if there’s enough there for him.”