By WILL WEISSERT and SEUNG MIN KIM (Associated Press) WASHINGTON (AP) — Joe Biden opened his 2020 presidential run at a Pittsburgh union hall, declaring, “I’m a union man. Period.” As he gears up for reelection, the president’s first political rally is being held at a union gathering on the other side of Pennsylvania, punctuating just how much Biden is counting on labor support to carry him to a second term — especially in a critical battleground state. The symmetry is no accident.