open (up) daylight v. phr. especially in horse racing, to out-distance a competitor. (source: Double-Tongued Dictionary)
Further reading
Need a slang term that can replace just about any noun? Try chumpie. If you’re from Philadelphia, you may already know this handy placeholder word. And there’s Queens, Brooklyn, Staten Island, Manhattan, and … The Bronx — why do we add...
The expression to go chalk has to do with rankings in an athletic tournament and harks back to when seeded teams or players were listed on a chalkboard. To pick chalk means to choose one’s favorite competitor, and you can also speak of a chalk...