Thursday Night's GOP Debate Could Get Nasty

There are a few simmering conflicts to watch out for in Thursday's Republican presidential debate. Well, more than a few. Actually, the entire primary looks like the brawl from "Anchorman" right about now, setting up what's likely to be a tense gathering in North Charleston, South Carolina, for Thursday's Fox Business debate.

Jeb Bush, Marco Rubio, and Chris Christie are clawing at each other to get to the top of the establishment heap. Donald Trump and Ted Cruz, who kept a long running truce until recently, are now in an ugly fight to win more revolution-minded conservatives. And Cruz and Rubio have spent much of the last month in a grudge match of their own over their own crossover voters.

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A bunch of factors have conspired to make the fighting particularly nasty in the home stretch before Iowa's Feb. 1 caucus — relative parity in the polls between the candidates, Donald Trump, a flood of super PAC money, widening ideological divisions within the party, Donald Trump again. Whatever the cause, you can expect many of the following disputes to come up on Thursday.

The Establishment Stalemate

The contest to consolidate moderate Republicans and "establishment" supporters between Rubio, Bush, Christie, and Ohio Gov. John Kasich resembles a bucket of crabs. Every time one of them looks like they might finally climb to freedom, another one grabs them with their pincers and drags them back into the pile.

Everyone is fighting for a decent showing in Iowa and either first place behind Trump or a strong second in New Hampshire in the hopes it will knock the rest out for good. For a while, it looked like Rubio was on the precipice of breaking out and taking that position ahead of schedule. But that attracted a wave of attacks from the rest of the field — on everything from his policies, to his work ethic, to his appearance — that now are only getting nastier.

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Right now, Bush's super PAC Right to Rise, which has spent more than $52 million on commercials (by far the most of any group or campaign), is pouring money into anti-Rubio ads and videos. One new spot depicts him as a human weathervane on immigration and accuses him of changing his position on "amnesty" to back a "path to citizenship" bill in the Senate before abandoning his own legislation. The irony, of course, is that Bush is arguably the most pro-reform candidate in the field on immigration. Another web video, playing to the same flip-flop theme, makes fun of Rubio's fashionable heeled boots, which several rivals have also highlighted as an important example of something or other.

Christie, who has substantially improved his reputation with GOP voters in recent polls, is also throwing punches at Rubio. Recently, he joked that the "truant officer" was out for Rubio over his regular missed votes in the Senate and said that Hillary Clinton would "cut his heart out" in a general election.

He's also gone after Bush, arguing he had an easy time as governor compared to his own stint in New Jersey: "You know, being prepared for the White House?" Christie told MSNBC last week. "He's not. He's just not."

RELATED: New Iowa poll shows Cruz, Trump battling for top spot

Rubio and his supporters are doling out plenty of attacks themselves. Pro-Rubio Conservative Solutions PAC is turning out new ads depicting Christie as President Obama's "favorite Republican" and reminding voters of the Bridgegate scandal, in which emails showed two of the governor's top aides celebrating an artificial traffic jam that was concocted to wreak vengeance on a mayor who crossed their boss. Christie has denied any involvement in the incident and no evidence has emerged to link him to the traffic scheme. Rubio has also accused Christie of donating to Planned Parenthood in the 1990s, which Christie now claims was based on a "misquote" in an old story. (Fun fact: The reporter who quoted him is now Christie's spokesman.)

The Conservative Quagmire

Over on the anti-establishment side of the ledger, Trump and Cruz have finally abandoned their buddy act and are in open warfare. As is usually the case with fights involving Trump, the conflict has grown very nasty very quickly.

Trump's main argument against Cruz is that he might not be eligible to be president because he was born in Canada and the Constitution requires the commander in chief to be a "natural born" citizen. It's a less conspiratorial twist on his longtime accusation that Obama was ineligible based on phony allegations that the president was born in Kenya and not his actual birthplace of Hawaii.

RELATED: Ted Cruz slams New Yorkers, but doesn't he want their votes?

"He's going to be running and people are going to be suing to say that he's not allowed to run," Trump said in an interview with MSNBC on Wednesday.

Cruz isn't the first candidate to run for president despite being born abroad — George Romney, Mitt's father, was born in Mexico - and many mainstream legal scholars argue that the Constitutional provision only means that the president had to have been a citizen at birth, which Cruz was by dint of his American mother. (He even produced her birth certificate this month to prove it.) But Trump has gotten some non-Trumpian figures to at least acknowledge questions about Cruz's qualifications, including Cruz's old Harvard professor Laurence Tribe and Sen. John McCain, who was born in the American zone of the Panama Canal.

Abandoning his pacifist approach to Trump, Cruz responded this week by subtly suggesting Trump's eligibility concerns are part of a liberal plot.

"It is more than a little strange to see Donald relying on his authoritative a liberal, left wing judicial activist Harvard law professor, who is a huge Hillary supporter," Cruz said in Iowa, a reference to Tribe's doubts about his eligibility. "It starts to make you think, gosh, why are Hillary's strongest supporters backing Donald Trump?"

Cruz has also started accusing Trump of representing (gasp!) "New York values" as opposed to the strict moral code favored by the good people who live in politically influential early primary states.

"The rest of the country knows exactly what New York values are," Cruz told Fox News host Megyn Kelly on Tuesday. "I got to say, they're not Iowa values and they're not New Hampshire values."

Finally, Cruz and Rubio are still engaged in a heated but usually more substantive argument over a variety of policy issues, including foreign policy, immigration, and now taxes. In recent days, Rubio has pointed out that Cruz's multi-trillion dollar tax plan would replace much of the current tax code with a giant tax on consumption. Rubio calls the tax a "dangerous expansion of Washington's power," Cruz calls it a more efficient business tax.

Add it all up and no one should be surprised if Thursday is one of the most combative debates of the primary for either side. The polls are tight, voters are paying attention, and everyone is running out of time to get their message across. Game on.

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