President Trump and Democratic nominee Joe Biden will spend the final days before the election campaigning across Pennsylvania, viewed by many as the potential tipping point in the race for 270 Electoral College votes.

Biden and running mate Sen. Kamala Harris (D-Calif.) will “fan out across all four corners of the state” on Monday as they seek to maximize turnout ahead of Nov. 3, the campaign says.

Trump will hold three rallies in Pennsylvania on Saturday, beginning in Bucks County in the eastern part of the state, working his way toward the middle with an event in Reading, and finishing out west, with a rally at the Pittsburgh-Butler Regional Airport. Trump also held three rallies in the state on Monday.

Trump carried Pennsylvania by less than 1 point in 2016, turning the state red for the first time since 1988. Trump is also defending Wisconsin and Michigan, the other two former “blue wall” states he flipped for the first time in decades in 2016. 

But Pennsylvania might be Trump’s best shot of the three, as most recent polls show Biden leading by 7 points or more in Michigan and by 5 points or more in Wisconsin.

The data is less clear in Pennsylvania, where Biden leads by 3.6 points in the RealClearPolitics average. The latest The Hill-Harris poll found Biden ahead by 5 points in the state. 

Republicans believe the president’s support is understated in Pennsylvania, which has large swaths of rural land in between Pittsburgh and Philadelphia.