John Lester (1:48.23 800) and Matt Strangio (4:03.57 mile) are the two big names here. Cruz Culpepper has dropped out due to soreness from last week's race in CO, kind of a shame because he probably had the best chance out of all of them to break 4.
https://www.milesplit.com/articles/282380-the-independence-day-showdown-sub-4-attempt-is-nearing