.NO PRESIDENTIAL controversy has had as much impact on a political election as that between Joe Biden and Donald Trump on June 27th. Mr Biden's performance was actually so tragic that his personal celebration pressed him to drop out. Since Kamala Harris, the vice-president, substituted him as the Democrats' candidate the ethnicity has tightened. It is right now a toss-up, according to The Economist's style. On September 10th Ms Harris will definitely encounter Mr Trump in a second presidential controversy. Just how much variation will this set create?