Open this photo in gallery: President Joe Biden speaks at a campaign event in Atlanta, Ga. on on March 9.Megan Varner/Getty Images With the Super Tuesday primaries in the rear-view mirror and a rematch between Donald Trump and Joe Biden set in motion, the U.S. presidential race now shifts into the normal rhythms of any election campaign. There will be barnstorming, promises, gaffes, polls, lies, half-truths and invented controversies, all of them devouring the front pages until the vote on Nov. 5. But this is anything but a normal election: it is, as Mr. Biden is trying to convince voters,...