Thomson Reuters
Republican U.S. presidential candidates pose before the start of the 2016 U.S. Republican presidential candidates debate held by CNBC in Boulder
Here are the candidates who will be on stage: Real-estate mogul Donald Trump, Sen. Ted Cruz (R-Texas), Sen. Marco Rubio (R-Florida), former Florida Gov. Jeb Bush (R), Sen. Rand Paul (R-Kentucky), retired neurosurgeon Ben Carson, Ohio Gov. John Kasich (R), New Jersey Gov. Chris Christie (R) and former Hewlett-Packard CEO Carly Fiorina.
For the second consecutive debate, former Arkansas Gov. Mike Huckabee (R) was relegated to an an earlier, "undercard" debate.
He he joined Sen. Lindsey Graham (R-South Carolina), former Sen. Rick Santorum (R-Pennsylvania), and former New York Gov. George Pataki (R).
The main affair could get chippy, as candidates look to improve their standings with fewer than 50 days before the first votes are cast in the primary process.
Debate coverage begins at 8:30 p.m. ET. Check back here for frequent updates.