Thursday marks the first Republican presidential debate of the new year, and it will feature a significantly whittled-down number of candidates. Fox Business Network announced Monday it would invite just seven GOP candidates to participate in its prime-time event Thursday night.

The main stage will feature Donald Trump, Texas Sen. Ted Cruz, Florida Sen. Marco Rubio, retired neurosurgeon Dr. Ben Carson, former Florida Gov. Jeb Bush, New Jersey Gov. Chris Christie and Ohio Gov. John Kasich. This lineup means that Kentucky Sen. Rand Paul and businesswoman Carly Fiorina were relegated to the undercard debate.

However, Paul, who has been on the main stage for the five previous debates, told CNN Monday he would boycott the early debate. “I won't participate in anything that's not first tier because we have a first-tier campaign,” Paul said.

The main debate will take place at 9 p.m. EST, and the undercard debate will take place at 6 p.m. EST. In addition to Paul and Fiorina, former Arkansas Gov. Mike Huckabee and former Pennsylvania Sen. Rick Santorum were invited to that debate.

To qualify for inclusion in the prime-time debate, candidates needed to be either among the top six in an average of the five most recent national polls or among the top five in an average of the five most recent Iowa or New Hampshire polls. Fox Business Network ultimately used six national polls because two polls were conducted concurrently.

Paul contended that he had finished fifth in a recent Iowa poll and placed higher in other polls, but he was in seventh place nationally and in the two early states as of Monday. For Fiorina, this debate will be a return to the undercard debate where she began her presidential bid. At the first GOP debate in August, she appeared on the early stage, but after her strong performance catapulted her to the main event, she has failed to take advantage of the increased attention.

The early debate will be moderated by Fox Business Network anchors Trish Regan and Sandra Smith, the network said in a statement about the event, and the main showdown will be moderated by anchors Neil Cavuto and Maria Bartiromo, who moderated the last FBN debate.