Three big risks that might tip America’s presidential election

And so it is confirmed. After Super Tuesday, it seems clear that the presidential election of 2024 will be a rematch—the first time a former president has challenged a sitting one since 1912. The candidates are exceptionally well-known, yet about 12% of voters have yet to choose between them. Those swing voters may decide what is shaping up to be a tight race. In the six elections before the year 2000, the average margin of victory in the popular vote was nine points. In the six since 2000 it has been three points. Even that understates how close presidential elections are these days. Just six states will be competitive in November. Last time round 160m Americans voted, but Joe Biden won Wisconsin, the tipping-point state, by 20,000 votes, or 0.013% of the total votes cast. When elections are this close, small differences in the inputs can have world-changing effects.