The GOP presidential debates take place Wednesday night at the Reagan Presidential Library in Simi Valley, Calif.
The 16 Republican candidates are poised to take the stage for the marathon pair of debates, President Ronald Reagan's plane at their backs and a trio of questioners before them.
First up: Four candidates who did not qualify for the top-tier group debating later. They are former Sen. Rick Santorum, former New York Gov. George Pataki, Louisiana Gov. Bobby Jindal and South Carolina Sen. Lindsey Graham.
Some of what they say, if interesting enough, could be played at the later debate between 11 hopefuls who performed better in the polls, according to sponsor CNN.
The main event includes 10 men and one woman -- business executive Carly Fiorina -- arrayed shoulder-to-shoulder. At center, front-runner Donald Trump. On either side: retired neurosurgeon Ben Carson and former Florida Gov. Jeb Bush. The others will be arrayed outward, with Kentucky Sen. Rand Paul and New Jersey Gov. Chris Christie at the ends.
Altogether, the event is expected to last about five hours.