REUTERS/Mike Blake
Donald Trump, left, and Sen. Ted Cruz (R-Texas).
Here's who will be on stage: Front-runner Donald Trump, US Sens. Ted Cruz (R-Texas) and Marco Rubio (R-Florida), retired neurosurgeon Ben Carson, Gov. Chris Christie (R-New Jersey), former Florida Gov. Jeb Bush, Gov. John Kasich (R-Ohio), and former Florida Gov. Jeb Bush.
The debate comes as the rhetorical barbs between once-friendly candidates have increased significantly.
Bush has kept up his attacks on Trump, explaining to audiences at campaign events why he thinks Trump is a "jerk."
"Do you want a president who disparages women? Muslims of all kinds, people with disabilities, Hispanics - I mean, we're getting down to about 90% of all people here," Bush said last Wednesday. "I mean at what point do we say, 'Enough of this?'"
For his part, Trump has focused his attacks on Cruz, a surging rival, raising questions about the senator's eligibility to be president considering that he was born in Canada.
Check back with Business Insider for updates throughout the night.