President Donald Trump will make an official White House visit to a medical manufacturing plant in Guilford on Friday, his first trip to Maine since taking office and a seismic event for a town of 1,500 in the state’s least populous and most conservative county. The president’s trip to Puritan Medical Products, one of the world’s top makers of the medical swabs used in coronavirus testing, comes amid nationwide unrest over police brutality and a global pandemic that has killed more than 100,000 people in the United States. For Trump, who made five visits to Maine during the 2016 campaign, the visit also offers a window into the kind of politics that made him successful that year — his disdain for foreign trade, his promotion of American manufacturing and his electoral success in more rural, historically Democratic areas, most of which he will need to hold onto this year if he hopes to stay in office. Trump won Maine’s 2nd Congressional District and its single electoral vote by 10 points in 2016, with his promises to bring back manufacturing jobs back resonating in a region that had seen more than two decades of mill closures. But the district, one of 21 that flipped from favoring former President Barack Obama in 2012 to Trump in 2016, is expected to be another battleground this year.