5 Things to Watch for at 6th GOP Presidential Debate

The first Republican debate of 2016 takes place tonight in South Carolina, just 18 days before the Iowa caucuses.

Hosted by the Fox Business Network, the debate will feature seven candidates: Donald Trump, Ted Cruz, Marco Rubio, Ben Carson, Jeb Bush, Chris Christie and John Kasich.

Here are five things to watch when the Republicans take the stage:

Will Trump Take on Cruz?Republican front-runner Donald Trump said in an interview Wednesday, "I'm not going to attack anybody that I know, but if they attack me, I'll attack them back times five."

The big question: Does that apply to Ted Cruz?

Since Cruz has become a bigger threat -- especially in Iowa -- Trump has stopped playing nice and has started questioning the Canadian-born Cruz's eligibility to be president. For his part, Cruz said he is "not interested in throwing rocks" at Trump.

A Loan to RememberThe New York Times reported Wednesday that Cruz did not properly disclose a loan from Goldman Sachs he used to fund his Senate run. Cruz addressed the controversy Wednesday, calling it a "technical and inadvertent filing error" and his press secretary said they've reached out to the Federal Election Commission to see whether they need to amend their filings. The misstep could leave Cruz fighting a multi-front war tonight, with the loan -- as well as the citizenship issue -- likely to become a talking point for the moderators and the candidates.

Battle of the GovernorsChris Christie, John Kasich and Jeb Bush -- two current and one former governor -- are all hovering in the single-digits nationally and are looking to New Hampshire as the state that will likely make or break their candidacies.

Among the three, there may be only one ticket out of the Granite State. Will this game of survivor play out on the debate stage?

The Marco MomentMarco Rubio has held his own in past debates and he's considered the establishment favorite, though he hasn't seen a big jump in polling. What will the Florida senator do to stand out?

One possibility: Be more aggressive against his rivals. A new website paid for by the Rubio campaign, for example, bashes Cruz's economic plan, saying it will impose a "large new European style tax." He may also go after Christie and Bush for supporting an Internet sales tax.

Will Anyone Miss Rand Paul?Rand Paul, a candidate familiar with the main stage, was demoted to the undercard debate because of slumping poll numbers. In response, Paul has said he won't show up in Charleston at all.

"By any reasonable criteria, Sen. Paul has a top-tier campaign," his campaign said in a statement Monday night. "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."