This example was set up to demonstrate how the method works with a known electorate. The true outcome is a Harris win with 50.5% of about 1.4 million votes.

All data are rounded down, which is why a value of 50% indicates a Democrat win.

Below is a chart that shows the probability distribution of the Democrats' head-to-head vote share in based on pollsters that are well-rated by 538 since the Sept 10 presidential debate. Vertical black lines indicate a roughly 95% confidence interval.

Polling Data

Credit to 538 for their incredibly generous sharing of aggregate 2024 polling data.

Pollster	Poll Date	Pollster Rating	Popular Vote		Head to Head
Example	Oct 23 - 23		Harris51.7%	Trump48.3%	Harris51.7%	Trump48.3%
Example	Oct 21 - 21		Harris49.7%	Trump50.3%	Harris49.7%	Trump50.3%
Example	Oct 21 - 21		Harris52%	Trump48%	Harris52%	Trump48%
Example	Oct 18 - 18		Harris51.5%	Trump48.5%	Harris51.5%	Trump48.5%
Example	Oct 18 - 18		Harris50.6%	Trump49.4%	Harris50.6%	Trump49.4%
Example	Oct 15 - 15		Harris54.9%	Trump45.1%	Harris54.9%	Trump45.1%
Example	Oct 15 - 15		Harris52.2%	Trump47.8%	Harris52.2%	Trump47.8%
Example	Oct 12 - 12		Harris51.2%	Trump48.8%	Harris51.2%	Trump48.8%
Example	Oct 09 - 09		Harris51.5%	Trump48.5%	Harris51.5%	Trump48.5%
Example	Oct 06 - 06		Harris50.7%	Trump49.3%	Harris50.7%	Trump49.3%
Example	Oct 06 - 06		Harris50.1%	Trump49.9%	Harris50.1%	Trump49.9%
Example	Oct 03 - 03		Harris50.2%	Trump49.8%	Harris50.2%	Trump49.8%
Example	Oct 01 - 01		Harris50%	Trump50%	Harris50%	Trump50%
Example	Sep 29 - 29		Harris48.3%	Trump51.7%	Harris48.3%	Trump51.7%
Example	Sep 29 - 29		Harris47.1%	Trump52.9%	Harris47.1%	Trump52.9%
Example	Sep 25 - 25		Harris51.3%	Trump48.7%	Harris51.3%	Trump48.7%
Example	Sep 25 - 25		Harris51.2%	Trump48.8%	Harris51.2%	Trump48.8%
Example	Sep 22 - 22		Harris49.4%	Trump50.6%	Harris49.4%	Trump50.6%
Example	Sep 19 - 19		Harris51.1%	Trump48.9%	Harris51.1%	Trump48.9%
Example	Sep 19 - 19		Harris49.3%	Trump50.7%	Harris49.3%	Trump50.7%
Example	Sep 16 - 16		Harris51.5%	Trump48.5%	Harris51.5%	Trump48.5%
Example	Sep 16 - 16		Harris51.9%	Trump48.1%	Harris51.9%	Trump48.1%
Example	Sep 14 - 14		Harris51.5%	Trump48.5%	Harris51.5%	Trump48.5%
Example	Sep 14 - 14		Harris50%	Trump50%	Harris50%	Trump50%