In 2016, Donald Trump tore down Democrats´ “blue wall,” winning the White House with surprise victories in Michigan, Pennsylvania and Wisconsin. This year, Joe Biden is trying to rebuild. The Democratic presidential nominee’s first pandemic-era campaign trips beyond his home in Delaware are taking him to all three states, an indication of how closely Biden’s electoral prospects are tied to his ability to flip those political battlegrounds.Last week, Biden traveled to Wisconsin and was followed quickly by running mate Kamala Harris, who held her own events there on Labor Day. On Wednesday, Biden heads to Michigan to tout a plan for boosting US manufacturing. He also has two stops scheduled this week in Pennsylvania. Though the Biden campaign often emphasizes that it sees multiple ways to secure the 270 Electoral College votes they need to win in November, the quickest path runs through Michigan, Pennsylvania and Wisconsin. “If Biden wins any of them – but particularly any two, with some of the other states that are in play – it´s pretty impossible for Trump to win the Electoral College,” said veteran Democratic strategist Joe Trippi.