(CNN)Hillary Clinton defeated Bernie Sanders in Nevada, suggesting her firewall could be secure. Meanwhile, Republicans in South Carolina are voting in the first-in-the-South primary. Results from both will tell us much about the future of the race and the strength of the contenders.
What we learned in Nevada, what to watch in South Carolina
Here's what to watch and what we've learned so far on Saturday.
Sanders surpassed expectations in New Hampshire by delivering a wallop to Clinton after nearly tying her in Iowa. But his defeat in Nevada -- Clinton led 52% to 47% with three quarters of the vote counted -- suggests the senator from Vermont needs some organizational prowess to match the excitement he has created among younger and more liberal voters if he is to deliver a true, long-term challenge to the former secretary of state.
The win was anything but assured heading into the Saturday contest. Clinton's campaign initially projected confidence in Nevada, pointing to her appeal to the state's Latino voting population, but after New Hampshire, her team softened the rhetoric about the western state. Clinton's wins means she can begin to firm up the conventional wisdom that she still is the inevitable nominee.
Businessman Donald Trump has held a consistent polling lead among South Carolina Republicans that is likely to carry him to first place there. If the polls hold up, that could make the race for runner-up the biggest surprise coming out of the primary.
The Republican race for the nomination is increasingly looking like a three-man race between Trump, Florida Sen. Marco Rubio and Texas Sen. Ted Cruz. A second-place finish between the senators will help give them a leg up in the upcoming contests, although a third-place finish won't knock either of them out, either.
Coming in behind Trump will allow the runner-up to present himself as the alternative to Trump.
"The World Trade Center came down during the reign of George Bush," Trump said Saturday during the CBS debate in Greenville. "That's not keeping us safe. ... George Bush made a mistake. We can make mistakes. But that one was a beauty. We should have never been in Iraq. We have destabilized the Middle East."
Trump's comments elicited a boisterous negative response from audience members in the hall and provided an opening for other candidates to criticize him.
South Carolina is home to eight military bases and tens of thousands of veterans. Will Trump's outspoken assessment that their sacrifices in the wars of the past 15 years were part of a "mistake" hurt his appeal and soften his lead?
Also, will Trump's apparent support for the Iraq War in a September 2002 interview with Howard Stern -- which surfaced late Thursday and seemed to contradict his oft-repeated claim that he opposed the war since before it began -- hurt him with voters?
"Yeah, I may have," Trump said in a CNN Republican presidential town hall hosted by Anderson Cooper when asked if he had signaled to Stern that he was in favor of invading Iraq. "By the time the war started I was against it. And shortly thereafter, I was really against it."
He added that at the time he "was not a politician."
Bush has poured just about everything he's got in South Carolina. He's spent millions. He flew in his family, including his mother and his brother, George W. Bush, who has remained off the campaign trail until now. While he was able to secure the endorsement from South Carolina Republican Sen. Lindsey Graham, other key GOP figures in the state have looked elsewhere: South Carolina Gov. Nikki Haley, Sen. Tim Scott and Rep. Trey Gowdy, all influential leaders in the state, have endorsed Rubio.
Bush and his allies have set high expectations in the state by calling it "Bush country," so a poor showing would reinforce the notion that he has failed to inspire the Republican electorate, especially after failing to come close to achieving top-tier results in Iowa and New Hampshire, where he came in sixth and fourth, respectively.
Coming in a distant fourth in South Carolina will send him limping into Nevada, where the most recent CNN/ORC survey puts him at just 1%.
Bush has said he intends to continue regardless of the results Saturday, but he's banking on a strong showing here.