Welcome to Election Day. Tens of millions of Americans are expected to head to the polls to decide whether Republican President Trump or Democrat Joe Biden should occupy the White House for the next four years, as well as determine control of the Senate and House and 11 governor's mansions. Coronavirus has spurred an unprecedented shift to mail-in voting and prompted warnings from election officials that the tally could take longer to complete. The election results will also test if polls got it right this time, or if they will understate Mr. Trump's support.