President Biden would expand his 2020 margin of victory over former President Donald Trump if a rematch were held today, according to a new poll exclusively shared with The Post Wednesday. The WPA Intelligence survey of 1,571 registered voters found Biden, 80, leading 76-year-old Trump 47% to 40%. By comparison, Biden defeated Trump by 4.5 percentage points in the 2020 popular vote, while former President Barack Obama won re-election over Republican Mitt Romney by 3.9 percentage points in 2012. The poll, which has a margin of error of plus or minus 2.5% and was conducted between May 10 and 13,...