Fox Business Network on Monday announced the candidate lineup for the Jan. 14 Republican presidential debates – and already one candidate has said he will not participate after not qualifying for the prime-time event.

The participants qualifying for the prime-time, 9 p.m. ET debate are:

Billionaire businessman Donald Trump; Texas Sen. Ted Cruz; Florida Sen. Marco Rubio; retired neurosurgeon Ben Carson; New Jersey Gov. Chris Christie; former Florida Gov. Jeb Bush; and Ohio Gov. John Kasich.

The participants qualifying for the earlier, 6 p.m. ET debate are:

Kentucky Sen. Rand Paul; former HP CEO Carly Fiorina; former Arkansas Gov. Mike Huckabee; and former Pennsylvania Sen. Rick Santorum.

However, the Paul campaign said Monday night it does not plan to participate.

This is the first time Paul has not qualified for a prime-time debate and his campaign, within minutes of the announcement, issued a statement complaining about the criteria.

“By any reasonable criteria Senator Paul has a top tier campaign,” his campaign said. “He will not let the media decide the tiers of this race and will instead take his message directly to the voters of New Hampshire and Iowa.”

The FBN debate lineup was decided based on the results of national, New Hampshire and Iowa polling. To qualify for the prime-time debate, a candidate had to place in the top six in an average of recent national polls, or in the top five in an average of recent Iowa or New Hampshire polls. ‎

The debate comes as front-runner Trump faces a rising challenge from Cruz, particularly in the caucus state of Iowa where the two are effectively tied for the lead.

The changing dynamic has fueled new tensions in the race, with Trump now openly questioning whether Cruz’ Canadian birth complicates his eligibility to run.

Trump’s comments have opened the door to other candidates and lawmakers exploring the issue – though Trump insists he’s only bringing it up because he’s concerned Democrats could use the issue against his GOP rival.

“I really don't know,” Trump told “Fox News Sunday.” “Does natural born mean born to the land? In that case he's not. But nobody knows what it means. … I speak well of Ted. I'm only saying that Ted has to get this problem solved because if he's running against a Democrat, and they bring a lawsuit, he's got a hell of a thing over his head.”

Cruz has brushed off calls to seek a court judgment on the issue.

“The son of a U.S. citizen born abroad is a natural-born citizen,” Cruz said in a CNN “State of the Union” interview aired Sunday. “The internet has all sorts of fevered swamp theories.”

Legal scholars have backed Cruz in saying he would qualify as a natural-born citizen, and therefore be eligible to run, because his mother is an American citizen.

Nationally, Trump enjoys a more comfortable lead, but an interesting and fluid race is developing in early-voting New Hampshire where several candidates are in a tight battle for the No. 2 slot behind Trump – and many voters remain undecided.

The latest Fox News poll showed Trump leads with 33 percent among New Hampshire Republican primary voters – behind him are Rubio at 15 percent, Cruz at 12 percent, Bush at 9 percent and Kasich at 7 percent.

The Thursday debates will be held at the North Charleston Coliseum and Performing Arts Center in North Charleston, S.C.

Anchor/Managing Editor of Business News Neil Cavuto and Anchor/Global Markets Editor Maria Bartiromo will moderate the prime-time debate; anchors Trish Regan and Sandra Smith will moderate the first debate.