Sen. Tim Scott (R-SC) peaks through the curtain at a rally for Sen. Marco Rubio in Columbia, S.C., Feb. 19, 2016. 
Photo by Mark Peterson/Redux for MSNBC

Four things to watch for in South Carolina’s GOP primary

Updated

South Carolina’s Republican primary is Saturday, and the results will go an enormous way toward clarifying where the race stands.

Will Donald Trump solidify his support or show cracks in the foundation? Will the state be the first victory for Sen. Ted Cruz’s Southern-focused approach or the state that exposes its weakness? Will Sen. Marco Rubio finally break away from former Florida Gov. Jeb Bush and Ohio Gov. John Kasich, or is the establishment pileup set to continue?

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We’ll know a lot more about all the candidates come Saturday night. Here are four big stories to watch as the results pour in.

Donald Trump’s heat check

For Trump, South Carolina is a crucial test of just how far he can break with Republican orthodoxy and still win Republican votes.

The expectations for Trump in the state are clear. After leading polls for months, usually by double-digit margins, anything less than a solid win would be a disappointment.  Most polls show Trump as strong as ever, but one NBC/WSJ survey released Friday found his lead slipping to single digits over Cruz.

While his front-runner status is assured, Trump isn’t playing things safe. In fact, he seems determined to violate every taboo he can find in the party before voting begins.

In the last week, he’s accused former President George W. Bush of lying about Iraq intelligence to push the country into war, blamed House Speaker Paul Ryan for losing the 2012 election by proposing to cut Medicare and suggested he would keep a health insurance mandate – one of the most hated parts of the Affordable Care Act on the right – in his replacement plan (he later said he was misunderstood). 

Along the way, he also feuded with Pope Francis, who suggested Trump was “not Christian” over his immigration policy, and got caught in an apparent lie over his unsubstantiated boast that he opposed the Iraq War in 2003 after an old interview surfaced in which he called for an invasion.  

He finally closed in South Carolina on Friday night with a speech in which he praised torture and favorably recited an apocryphal story about Gen. John Pershing executing Muslim prisoners with bullets dipped in pig blood in the 1900s.  

If he can make it out of South Carolina untouched, he may be unstoppable. The next stretch of the calendar includes a slate of Southern contests on March 1, and delegate rules favor him so long as the field remains divided.

Ted Cruz’s Southern strategy

Cruz won the Iowa caucus thanks to heavy turnout from social conservatives, and his campaign boasted afterward the same formula that worked there would work in other evangelical-heavy states like South Carolina and beyond.

But the plan won’t work if Trump keeps beating him. And it especially won’t work if Cruz can’t narrow the field and gain on Trump before the March 1 race, which consists almost entirely of states that fit Cruz’s strategy. If he can’t perform well in South Carolina, it will be a flashing red sign that his theory of the nomination is flawed.

He’s leaving nothing on the table, though. Cruz is attacking Trump constantly over his past support for abortion rights and even held a press conference daring the billionaire to sue him over ads featuring Trump describing his “pro-choice” views in  a 1999 interview. His campaign is also running the most brutal anti-Rubio ads of the cycle, including a striking spot in which the senator and President Obama use similar language to explain the bipartisan immigration bill that Rubio co-authored and then abandoned.

One area where Cruz might grow support is by picking up supporters from Dr. Ben Carson, who has generated little buzz in South Carolina despite his natural connection to religious conservatives. If Carson fails to make an impact, he could fade out of the race entirely.

Marco Rubio goes for the knockout against Jeb Bush

South Carolina is make-or-break for Bush. After surviving New Hampshire thanks mostly to Rubio’s debate meltdown, his campaign identified South Carolina as an opportunity to show he has momentum of his own.

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Despite the help of his brother, George W. Bush, on the trail and on the air, his campaign appears to be struggling, and both Bush and his supporters sound frustrated on the trail.

Rubio, on the other hand, seems to have everything going his way in the final stretch. Gov. Nikki Haley endorsed him on Wednesday, Sen. Tim Scott and Rep. Trey Gowdy backed him earlier, and he earned favorable reviews in Saturday’s debate. He’s using his high-profile backers to make a broader case that he can unify the party’s warring factions while appealing to voters outside the GOP in November.

The downside for Rubio is that the raft of establishment backing raises expectations even higher. If he can’t crack second place in South Carolina, he could end up stuck in neutral while Trump and Cruz race toward the nomination. For all the hype, Rubio’s polling in the state is fairly unimpressive so far, and some surveys show Bush not far behind.

The upside is that Rubio can take a major step toward consolidating establishment support if he can just outperform Bush by a significant margin. If Bush sinks on Saturday, it’s likely he’ll face tremendous pressure from the party to exit the race before March 1 and give Rubio a chance to block Cruz and Trump.

John Kasich’s lottery ticket  

Lurking in the background of the Rubio/Bush fight is Kasich.

Despite coming in second place in New Hampshire, Kasich hasn’t garnered the same attention for his performance as Rubio and even Bush. There’s tremendous skepticism as to whether his message of folksy bipartisanship and his limited campaign apparatus can survive beyond the Granite State, where he succeeded by camping out for months.

His campaign did not declare South Carolina a top priority, pointing instead to Michigan’s March 8 contest as his next do-or-die moment. Nonetheless, he’s won endorsements from major state papers and earned glowing press on Thursday after an emotional town hall in which he hugged a supporter who had suffered through personal tragedy.

If Rubio and Bush fail to impress and Kasich puts in a surprise showing, maybe even just double-digit support, he could move up in the national conversation. That would be good news for Kasich, but also create even more heartburn for Republicans who are hoping to winnow the field as soon as possible to keep Trump or Cruz from racking up a delegate lead in March.

Photos: South Carolina's Republican presidential primary
Republican presidential candidates have been campaigning across the Palmetto State in anticipation of its first-in-the-South GOP primary.

Donald Trump, Jeb Bush, John Kasich, Marco Rubio, South Carolina and Ted Cruz

Four things to watch for in South Carolina’s GOP primary

Updated