.NO PRESIDENTIAL controversy has possessed as much impact on an election as that in between Joe Biden and Donald Trump on June 27th. Mr Biden's performance was so disastrous that his very own party pushed him to quit. Because Kamala Harris, the vice-president, changed him as the Democrats' nominee the race has actually tightened up. It is currently a toss-up, depending on to The Economist's style. On September 10th Ms Harris will certainly experience Mr Trump in a 2nd presidential discussion. Just how much distinction will this set help make?