Horses -- December 2, 2025

AI prompt: I have two different sources talking about the "best" race horse ever, with regard to progency. These were both in the mid-19th century. One was Lexington (name of the horse) and the other was "Electioneer" -- a Leland Stanford horse. Is this an "apple-to-apple" comparison or two different classes of horse?

Google search:

Two sources in my library:

• Lexington: The Extraordinary Life And Turbulent Times of America's Legendary Racehorse, Kim Wickens, c. 2023. Link here. 
• Palo Alto: A History of California, Capitalism, and The World, Malcolm Harris, c. 2023. Link here.