Republican presidential nominee Donald Trump, whose campaign has identified Pennsylvania and two other states as must-wins in November, will hold a rally in Mechanicsburg tonight.

The billionaire real-estate developer and television star will make an appearance at Cumberland Valley High School. The event, which is free and open to the public, begins at 7 p.m. Doors open at 4 p.m. Cumberland Valley High School is located at 6746 Carlisle Pike, Mechanicsburg.

Trump and Democratic presidential nominee Hillary Clinton have both made numerous appearances in the Keystone State already in hopes of securing its 20 electoral votes in November.

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Pennsylvania is one of three states Trump is focusing on as he confronts "a daunting electoral map and a significant financial disadvantage," as The New York Times reported this weekend.

His campaign, the newspaper reported, "is preparing to fall back from an expansive national campaign and concentrate the bulk of his time and money on just three or four states that his campaign believes he must sweep in order to win the presidency."

Reports The Times:

"Even as Mr. Trump has ticked up in national polls in recent weeks, senior Republicans say his path to the 270 Electoral College votes needed for election has remained narrow — and may have grown even more precarious. It now looks exceedingly difficult for him to assemble even the barest Electoral College majority without beating Hillary Clinton in a trifecta of the biggest swing states: Florida, Ohio and Pennsylvania."

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