What is chalk in betting?

The heavy favorite. "Betting chalk" = always backing the likely thing.

From racetrack days when the favorite's odds got rewritten so often the chalkboard stayed dusty. Betting chalk feels safe, you win often, but at 90% prices a single miss erases nine wins.

Prediction-market chalk has a twist: favorites are historically slightly *underpriced* (the mirror of longshot bias), so disciplined chalk-betting can actually be sharp. The sin isn't backing favorites, it's overpaying for the comfort.