President Trump addresses a campaign rally in Montoursville, Pa., on Monday, May 20, 2019. (Carlos Barria/Reuters)

President Trump mocked former vice president Joe Biden for his views on trade and focus on foreign policy, taking aim Monday at the Democrat leading the polls in the state Biden has made his proving ground for defeating Trump next year.

The president touted an economic turnaround on his watch, saying Pennsylvania now has historically low unemployment that no political competitor could best.

“Sleepy Joe said that he’s running to, quote, ‘save the world,’ ” Trump said to laughter from supporters at a campaign rally here. “Well, he was: He was going to save every country but ours!”

Trump’s “Make America Great Again” rally at an airport hangar in this small north-central Pennsylvania town was nominally a show of support for Republican state Rep. Fred Keller, the heavy favorite in a special election Tuesday to fill the congressional seat vacated in January by Tom Marino, a Republican who had just been reelected to his fifth term.

Penn State professor Marc Friedenberg, who lost to Marino in 2018 by 32 points, is also the Democratic candidate this time.

Trump won the district by 36 points in 2016.

With Keller’s victory in this solidly Republican area all but assured, Trump’s visit was more about leveraging his strong support in the Republican midsection of Pennsylvania, where his overwhelming victory in 2016 powered him to a statewide win with a margin of less than 1 percent.

Trump will need to repeat or best that performance in 2020 to again take a state that voted Democratic in the six presidential elections before 2016. Pennsylvania, with 20 electoral college votes, is considered one of the best chances for a Democratic reversal in 2020.

“We gotta win this state,” Trump said to cheers. “We did great last time. Remember the fake polls they put out last time? Suppression — they call them suppression polls, ‘Pennsylvania will go for Hillary Clinton!’ ” Trump said, making an unfounded accusation that polls predicting his defeat here were orchestrated to help his opponent.

“Unfortunately for them, it didn’t happen.”

The crowd responded with a long chant of “Lock her up!” To which, Trump responded: “We have a great new attorney general who’s going to give it a very fair look.”

Trump also repeated his false rhetorical claim that “our country is full.”

“We don’t want people coming up here,” Trump said to cheers and chants of “Build that wall!”

Trump called a pan-Asia trade deal backed by Biden “a disaster” for Pennsylvania and singled out remarks Biden recently made about charting a new course with China.

“Remember he said a week ago, ‘China’s not a competitor.’ China’s not a competitor?” Trump exclaimed. “Hey, look. What they’ve done to us is indescribable, economically,” he said. “Our leaders allowed it to happen. Well, it’s not happening anymore. I ran, and we have made America great again, and we are going to keep America great.”

Biden has staked much of his early campaign message on the theory that he can deny Trump a repeat victory here. A native of working-class Scranton, more than an hour to the east, Biden inaugurated his 2020 campaign in Pennsylvania and is using Philadelphia as his campaign headquarters.

“Biden deserted you,” Trump said. “I guess he was born here, but he left you, he left you for another state.”

In the last of his kickoff speeches, on Saturday in Philadelphia, Biden spoke of the birth of American democracy in that city and toggled between attacks on Trump and calls for unity and civility.

“If the American people want a president to add to our division, lead with a clenched fist, closed hand, a hard heart, to demonize the opponents and spew hatred, they don’t need me,” Biden said. “They’ve got President Donald Trump.”

Biden lived in Pennsylvania for 10 years before moving with his family to Delaware, a state he represented in the U.S. Senate for 36 years.

Pennsylvania carries more electoral college votes than any of the other contested industrial Midwest states that Trump won last time.

“How many different ways can you say 20?” joked Franklin & Marshall College political science professor and Pennsylvania pollster G. Terry Madonna, referring to the state’s electoral college vote total.

Biden is prioritizing Pennsylvania as he tries to argue that he is in a unique position to deny Trump a victory among more socially conservative Democratic voters who abandoned the party in 2016, Madonna said.

Biden led Trump by double digits in a poll of Pennsylvania voters released last week that also had Biden swamping his next-nearest competitor for the Democratic nomination, Vermont Sen. Bernie Sanders (I), by more than 25 percentage points.

The Quinnipiac University poll showed Biden with 53 percent to Trump’s 42 percent in a hypothetical head-to-head matchup. The survey of 978 registered Pennsylvania voters was conducted May 9-14 and has a margin of error of plus or minus 4.2 percentage points.

More than half of Pennsylvania voters say they are better off financially than they were in 2016, the poll found. But despite strong U.S. economic performance, 54 percent of Pennsylvania voters overall disapprove of Trump’s job performance while 42 percent approve, the poll found.

Trump dismissed the polling Monday.

“I think we’re doing very well in Pennsylvania. We won it last time. The polls had us losing Pennsylvania last time, and we won,” he told reporters as he left the White House for the rally.

There was little sign of disapproval on the crowded streets of this small town. At a decaying mall where rallygoers boarded shuttle buses, vendors hawked T-shirts that read “Border Wall Construction Company” and “Build the Wall, Deport Them All,” alongside the usual “Make America Great Again” and “Trump-Pence” wares.

Trump won surrounding Lycoming County in 2016 with 69.6 percent of the vote, to Democrat Hillary Clinton’s 25.4 percent.

The rally had a festive feel, with chants of “U-S-A” and a pre-speech playlist that included the Rolling Stones and Luciano Pavarotti. Donald Trump Jr. was the principal warm-up act, mocking Biden and Biden’s son Hunter, among other Democrats.

The crowd cheered with delight when the campaign broadcast the voice of an air traffic controller tracking the approach of Air Force One.

Shortly after he began speaking, Trump spotted a supporter in the crowd wearing a suit in a brick-wall print. Trump brought the man onstage with a whoop.

“This is a very Republican area, and people are looking forward to the visit. I think most people in this area feel pretty positive” about the president, Montoursville Mayor Stephen Bagwell said in an interview before the visit.

Trump’s overall economic message plays well here, Bagwell said.

“I would not think that most people in this area have really had a significant change in the last few years, but people do feel pretty positive.”

Bagwell said he has not heard concern among his neighbors about potential price hikes on consumer goods or other items as a result of the president’s escalating tariff war with China.

Unemployment here was 4.3 percent in March, slightly above the state figure of 3.9 but down from roughly 6 percent at the start of Trump’s presidency.

Felicia Sonmez in Washington contributed to this report.