Former President Barack Obama is set to rally supporters of Vice President Kamala Harris on Thursday night in Pittsburgh as both presidential campaigns look to shore up their base ahead of the Nov. 5 election. Pennsylvania is a crucial battleground state, and along with Michigan and Wisconsin, is part of the so-called “blue wall” of three competitive states that are likely to decide the election. Obama won the state in both his 2008 and 2012 presidential races. The former president’s appearance on the campaign trail kicks off his swing-state blitz on behalf of the Harris-Waltz ticket, accordin…