DES MOINES — President Trump stunned the political universe in 2016 with a sweep of critical Northern swing states, winning Michigan, Pennsylvania and Wisconsin by less than one percentage point and forcing Democrats into four years of soul-searching about what went wrong in their historic geographic base.
Four years later, the chilly Midwest looms again as the principal battleground of the election, and on Friday Mr. Trump and former Vice President Joseph R. Biden Jr. crisscrossed the region campaigning in states that are not only must-win for the president but also central to the…
