Story highlights Just seven Republican candidates will appear on the main stage for Thursday night's GOP primary debate

Kentucky Sen. Rand Paul says he's skipping the invitation to the early debate

Washington (CNN) Rand Paul will boycott Thursday night's Republican primary debate in South Carolina after being relegated from the main stage, he said on Monday.

"I won't participate in anything that's not first tier because we have a first tier campaign," the Kentucky senator told CNN's Wolf Blitzer.

Paul's announcement came moments before Fox Business Network, the sponsor of Thursday's debate, announced that just seven candidates had qualified for the main stage. Those candidates are Donald Trump, Ben Carson, Ted Cruz, Marco Rubio, Chris Christie, Jeb Bush and John Kasich.

Both Paul and Carly Fiorina, who appeared on the main stage in last month's CNN debate, were relegated to the undercard round, along with Rick Santorum and Mike Huckabee, according to the network.

Fox Business announced last month that its January 14 debate would include the top six candidates based on the average of the five most recent national polls, as well as those who finish in the top five in Iowa or New Hampshire. Paul failed to meet that criteria.

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