Washington (CNN) Republican presidential contenders are set for one last nationally televised chance to make their cases before Saturday's crucial South Carolina primary.

The pair of town halls, which start at 8 p.m. on both Wednesday and Thursday nights, will be moderated by CNN's Anderson Cooper. The first night features Ben Carson, Ted Cruz and Marco Rubio, and the second night's lineup is Jeb Bush, John Kasich and Donald Trump.

Here are five things to watch:

Cruz's Trump problem

While South Carolina might not be do-or-die for Texas Sen. Ted Cruz, it's at least a crucial early test of his Southern strategy. And if he can't top the billionaire businessman there, he could struggle to top him anywhere.

Cruz could try to draw a hard contrast with Trump on Supreme Court appointments by arguing that Trump can't be trusted to appoint reliably conservative justices.

The centerpiece of that argument: abortion. Cruz warned of Trump's history of supporting abortion rights -- a position Trump says he's reversed -- in a five-minute, straight-to-camera video his campaign released Tuesday.

Watch for whether Cruz goes for the jugular, throwing the kitchen sink of past Trump statements at his rival.

He'll make his case against the backdrop of both Trump and Florida Sen. Marco Rubio repeatedly tagging Cruz as a liar, portraying him as malleable on issues like immigration. Cruz, whose entire brand is built on his rock-ribbed conservatism, will have to fight off those charges before they cause serious damage.

Who is Rubio's target?

More specifically: Will Rubio spend his time attacking Cruz or former Florida Gov. Jeb Bush? The answer flags whether Rubio is playing for second or third in the Palmetto State.

Cruz and Rubio have long been each others' foil on the campaign trail, with increasingly heated battles over immigration marking their debates -- Rubio got Cruz to yell at him in Spanish in the most recent one.

Bush, though, could be the more immediate threat. Rubio's former Florida politics mentor has brought out the big guns, using George W. Bush and his mother, Barbara Bush, on the campaign trail.

It's a big bet that South Carolina could catapult Bush past Rubio and into the lead "establishment" spot in the race by capitalizing on Ohio Gov. John Kasich's inability so far to play in the South.

Rubio, though, has multiple paths to more votes. Which one he chooses could be the biggest question of the Republican race right now.

The SCOTUS opening

Both parties' presidential candidates have spent less time criticizing the other party and more time lambasting each other since voters started casting ballots.

But the looming fight between President Barack Obama and Senate Republicans over how Obama's nominee to replace recently deceased Supreme Court Justice Antonin Scalia will bring those partisan divides back into focus.

Men who are running for the United States' most powerful office will have to defend their positions that the current officeholder's power should be limited.

It's a tricky topic, and it extends beyond a referendum on Obama to procedural questions such as whether the Senate Judiciary Committee should give his nominee a hearing and a vote.

The race's two senators, Cruz and Rubio, will both play real-life roles in deciding the issue's outcome.

Trump the risk-taker

Trump left New Hampshire with one blowout win under his belt and a hefty lead in South Carolina.

Then he risked it all, going hard after George W. Bush, accusing the last Republican president of failing to keep the country safe on 9/11 and bumbling his way into the war in Iraq, in a state whose electorate is known for being very pro-military.

Trump has exercised restraint on the campaign trail at times -- but he's known for a more freewheeling style. And the audience questions, sometimes hostile, that Trump could face in the town hall make for a potentially combustible environment.

It's already clear Trump will try to outshine his rivals. He doesn't appear in the CNN town hall until Thursday night, so on Wednesday, he'll be appearing in one hosted by MSNBC.

But Trump's ability -- and willingness -- to shake up the focus of the entire campaign with a single comment makes his appearance must-see TV.

Can Carson climb back in?

Ben Carson was a total non-factor in the last Republican presidential debate on CBS.

And yet: The latest CNN/ORC poll of South Carolina voters showed him climbing from 4% support among those surveyed before the debate to 11% afterward.

Carson appears to keep surviving -- and at times, climbing -- just by virtue of not being involved in the fights the other candidates are waging.

It's especially bad news for Cruz, because polls in Iowa showed that his ship rises as Carson's sinks.

With the additional room to breathe that a town hall offers candidates, Carson will try to make his case more strongly than he has been able to do so far in debates.

If he succeeds, he could get a second look among evangelical voters in South Carolina. It's all but certainly not going to be enough to help him win the state, but it could cause others -- particularly Cruz, whose campaign's tactics in Iowa angered Carson -- to lose it.