For what reason did KDKA (the first U.S. radio broadcast station) choose the date November 2, 1920, for their first on-air broadcast?

On November 2, 1920, station KDKA made the nation's first commercial broadcast (a term coined by Conrad himself [Dr. Frank Conrad]). They chose that date because it was election day, and the power of radio was proven when people could hear the results of the Harding-Cox presidential race before they read about it in the newspaper.

KDKA was a huge hit, inspiring other companies to take up broadcasting. In four years there were 600 commercial stations around the country.