Another big caucus day and primary night on Saturday, when Democrats go to their caucus sites in Nevada, and Republicans go to the polls in South Carolina. Here are five things we'll learn from the results:

1. Is insulting the Bush family — and getting into a fight with the pope — a good idea or not? Donald Trump has doubled down on almost everything in South Carolina. He called George W. Bush a liar in the last debate, causing the GOP establishment to gasp in horror. The Bushes are extremely popular in South Carolina, but Trump is counting on the loyalty of his supporters, who haven't been turned off by anything else he's said or done. By calling attention, again, to his opposition to the Iraq War, he might have been trying to encourage independents and Democrats to go vote in South Carolina's open primary. Then on Thursday, Trump waded into a fight with Pope Francis, who is a revered public figure — but not with conservatives and evangelicals, who view him as too liberal. Maybe that was another example of Trump acting crazy ... like a fox?

2. Is Marco Rubio back? After his disastrous performance in the New Hampshire debate, and his subsequent fifth-place finish there, Rubio seems poised for a comeback. He got the coveted endorsement of South Carolina Gov. Nikki Haley, and none of the other candidates filleted him in the Greenville CBS debate the way Chris Christie had in New Hampshire. The GOP establishment would like to coalesce around Rubio; they're just waiting for him to actually win somewhere. Expectations are very high now, and Rubio needs to come in a strong third or, better yet, surge past Ted Cruz for second place.

3. Is this the end for Jeb Bush? South Carolina could return the GOP field to the three-man race many thought had emerged from Iowa. If Bush fails to finish ahead of Rubio, he will be under tremendous pressure to stand down, and he might do that as early as Sunday.

4. Can Hillary Clinton rebound? The Clinton campaign has been busy lowering expectations for Nevada, even to the point of angering the top Democrat in the state, Harry Reid, when one spokesman stated — falsely — that the state is 80 percent white. In fact, the Democratic electorate in Nevada was only 65 percent white, according to 2008 entrance polls. But Nevada, with its small population of Democratic caucus-goers, is very hard to poll. And Clinton campaign manager Robby Mook told donors this week that Clinton could either win by a few points or lose — they have no idea which! Although Clinton would like to avoid another embarrassing loss, many Democrats say she can weather a loss in Nevada. South Carolina, where Democrats vote the following Saturday, is crucial for Clinton. She needs to win by a large margin in order to stop, or slow, Bernie Sanders' momentum.

5. Is Cruz really surging past Trump? The most interesting poll number of the week was the NBC/WSJ survey that showed Cruz 2 points ahead of Trump nationally. That's a first in a very long time. So far, this well-respected poll is the only national survey that shows Trump slipping behind Cruz. But if Cruz can place close to Trump in South Carolina, it might be a sign that Trump is a vulnerable front-runner, whose outrageous attacks and break-the-rules behavior is finally catching up to him.