.NO PRESIDENTIAL discussion has actually possessed as much impact on a vote-casting as that between Joe Biden and Donald Trump on June 27th. Mr Biden's performance was thus unfortunate that his personal gathering pressed him to quit. Since Kamala Harris, the vice-president, replaced him as the Democrats' nominee the nationality has actually secured. It is currently a toss-up, according to The Economist's model. On September 10th Ms Harris will experience Mr Trump in a second presidential debate. How much difference will this set produce?