Perry, who vaulted into the lead among GOP candidates within a month of his official entrance into the race, is making his debate debut. Among the others onstage will be former Massachusetts Gov. Mitt Romney, the previous front-runner, and Minnesota Rep. Michele Bachmann, the "tea party" favorite before Perry joined the race last month.
The debate, sponsored by NBC News and Politico, will be moderated by NBC anchor Brian Williams and Politico editor John Harris.
Live coverage of the debate by Tribune Washington bureau reporters James Oliphant and Michael Memoli and Los Angeles Times reporter Robin Abcarian will start at 5 p.m. PDT.