Here's What You Need to Know Before the Republican Debate Tonight

The Republican presidential candidates are heading to Charleston, South Carolina, to debate each other again Thursday night, nearly two weeks before the first voting of the election begins in Iowa. The debate will have fewer candidates than ever before on stage, with only seven participating in the main event that kicks off at 9pm ET — and it promises to be the most interesting Republican debate so far.

Kentucky Senator Rand Paul and Carly Fiorina found out on Monday they were disqualified from participating in the main debate tonight and would instead be relegated to the earlier "undercard" version, at 6pm. Paul especially was not pleased with the pity offer to join the earlier event, telling CNN on Monday, "I won't participate in anything that's not the first tier."

Paul might not be happy that tonight's affair is an exclusive one but the other candidates, not to mention viewers, should be. Fewer candidates on stage with more time to speak increases the likelihood that there will be an actual discussion of policy, rather than just an exchange of barbed sound bites, according to Bill Whalen, a Republican commentator and research fellow at the Hoover Institute.

One topic that will almost certainly come up tonight is gun control. The event is taking place in Charleston, where a mass shooter killed nine people at a black church six months ago. For this reason, Whalen says, "it would be malpractice not to talk about guns." It is also one week after President Obama unveiled his executive order on gun control, to which all of the candidates have expressed their vehement opposition.

A debate focusing on substance is one of the few remaining chances the candidates have to set themselves apart before the first states begin voting next month. In Iowa, that's on February 1, and Donald Trump and Texas Senator Ted Cruz are currently neck-and-neck in that state. New Hampshire's primary is next, on February 9; Trump is also leading and Marco Rubio is scrambling for second place, followed by Jeb Bush and Chris Christie close behind.

So if you're hoping for a bloodbath, tune in. The main fight to keep an eye on tonight will be Rubio versus pretty much everyone. The young Florida senator is entering the debate after weeks of fending off attacks on everything from his choice of footwear to his  credit cards to his shoddy attendance record in the Senate. Since he is the favored establishment candidate, he's facing pressure from the other establishment candidates who want to be him — namely Bush and Christie — as well as the anti-establishment ones, Cruz and Trump, who want to beat him. Attack ads from his rivals, including mostly from Super PACs supporting Cruz and Bush, have attempted to paint him as weak, inexperienced, and conciliatory to Democrats, as the Washington Post points out.

As the frontrunner and the angry human weathervane of this election, Trump will also dictate much of tonight's tone. Trump has spent the last several weeks going after Cruz, currently his closest rival, mostly on the question of his eligibility to be president. Cruz is also coming into tonight 24 hours after it emerged that he took several loans of hundreds of thousands of dollars from Goldman Sachs to fund his first Senate race, something he had not disclosed before. This revelation, first reported by the New York Times Wednesday night, will make it considerably harder for the Texas senator to maintain his image as a populist with a disdain for all things establishment, a cornerstone of his campaign.

Tonight might also be one of the last opportunities for Ben Carson and John Kasich to remind everyone they still exist. Kasich arguably never managed to get people to remember his name or how to actually pronounce it, but Carson was at the top of the Republican pack in the fall. But after months of dwindling poll numbers, a series of foreign policy blunders, and a very public staff shake-up in his campaign, the former neurosurgeon is now essentially an afterthought. The final blow to Carson HQ came on Monday, when nearly the entire New Hampshire staff of a pro-Carson Super PAC announced they were quitting to go volunteer for Ted Cruz.

And if any of the candidates don't get a chance to speak enough tonight, they'll have another opportunity to in the next Republican debate, in Iowa on January 28.

Follow Olivia Becker on Twitter:  @Obecker928