What is the origin of the idiom "front runner" and when to use it?

The origin of the idiom "front runner" is believed to have originated in the United States in the mid-19th century. The term originally referred to a person who led a horse race from the start, holding the lead position at the front of the pack of horses in a horse racing competition. Over time, the term "front runner" came to be used more broadly to describe anyone who is in the lead or expected to win in a competition or election. The phrase is now commonly used in politics, sports, and other competitive contexts.