Here are five takeaways from Super Saturday.
Trump remains the Republican presidential front-runner, but he didn't clean up on Saturday. His losses to Cruz in Maine -- where Gov. Paul LePage had endorsed him -- and Kansas give hope to other campaigns that a strong ground game can at least chip away at his delegate count.
Cruz's two victories over Trump on Saturday came as Republicans turned up the heat on the real estate mogul this week. On Thursday, former Republican presidential nominee Mitt Romney delivered a blistering speech in Utah decrying Trump's campaign, and a number of high-profile members of the national security community expressed concern about his lack of understanding of foreign affairs. The outcome could encourage them to keep searching for vulnerabilities to exploit.
Trump also took criticism from conservatives for skipping a scheduled appearance at the Conservative Political Action Conference, the largest annual gathering of right-wing activists. Instead of addressing the conference, Trump held a rally in Kansas, a state Texas Sen. Cruz won Saturday by a margin of two-to-one.
However, Trump's campaign demonstrated strength in the South, a region Cruz's campaign had pointed to as key to its strategy earlier in the race. Trump on Saturday won the caucuses in Kentucky and the delegate-rich primary in Louisiana.
In his remarks after results were announced, Trump took the opportunity to knock both Cruz and Rubio. He called on Rubio, a Florida senator, to drop out of the race before the all-important Florida primary March 15, and he even worked a dig into his explanation of Cruz's victory, making a reference to the Texas senator's country of birth: "He should do well in Maine, because it's very close to Canada."
2. Cruz builds his case
Cruz has defeated Trump in more state contests than any other competitor, and in regions as diverse as the South, Midwest and New England. The showing bolsters his argument that he's the only figure in the GOP who can take on the billionaire businessman.
It's a point Cruz made at a campaign event in Idaho Saturday, where he telegraphed that other candidates should drop out to let Republicans rally around him: "What we are seeing in Kansas is a manifestation of a real shift in momentum."
Cruz benefitted from the fact that three of the four contests on Saturday were caucuses and that only one allowed voters other than previously registered Republicans to participate. These types of votes play to his strong ground organization and his appeal to the more committed, conservative wing of the party.
Underscoring his appeal among this group, Cruz on Saturday also won a straw poll of staunchly conservative activists gathered for the Conservative Political Action Conference, a sign that the ideological right seems to be rallying around him.
Despite his strong showing on Saturday, Cruz still faces major hurdles in overcoming Trump in the delegate race. Future contests include a mix of primaries and caucuses, many of which are open to voters who are not already registered Republicans. Cruz will need a better performance in those "open" states than he has had in the past if he wants to win.
3. Sanders still a thorn in Clinton's side
After Saturday, Clinton still won't be able to shut Sanders out of the race for the Democratic presidential nomination, even though she pulled in another win Saturday and leads the delegate count.
The Vermont senator continues to pick up just enough victories around the country -- he took Nebraska and Kansas on Saturday -- to stay a relevant force. And his campaign war chest remains strong enough to push him forward, possibly for months.
In a statement after he won Nebraska, Sanders hammered this point home, saying it was contests like this one that will help propel his campaign into the summer.
"The win in Nebraska coupled with a double-digit victory in Kansas tonight will put us on a path toward victory. We've got the momentum, the energy and the excitement that will take us all the way to the Democratic National Convention in Philadelphia," Sanders said.
In a way, Sanders is doing the same thing to Clinton now that she did to then-Sen. Barack Obama in the 2008 race. Even though Obama was racking up more delegate wins with each vote, Clinton still had the support and donor firepower to keep the race going.
Now, Clinton will need to carry a string of states to prove she has the Democratic race locked down. And it will be hard for her to argue Sanders should bow out any time soon, since she resisted dropping out in 2008 even as the math turned more and more against her.
4. Clinton still wins more diverse states
Sanders's campaign tends to do better in states with large populations of white voters, while the former secretary of state has had more success in states where greater numbers of African-Americans participate. That trend continued Saturday, when Sanders won in Nebraska and Kansas, two states where more than 85% of the population is white.
Clinton, meanwhile, crushed Sanders in Louisiana, where more than 30% of the population is African-American.
The results will help bolster the Clinton campaign's insistence that there could be a cap on Sanders' ability to garner support as the race extends to other parts of the country.
Sanders has acknowledged that his campaign does poorly among Southern black voters but also projects confidence that he will do better.
"We got decimated," Sanders said on ABC's "This Week" of South Carolina, where Clinton beat him 74% to 26% last month.
But Sanders predicted that he would do much better with African-American voters outside the Deep South: "You're going to see us much better in New York state, where I think we have a shot to win, in California and in Michigan."
Sanders will have a chance to prove he's right very soon, as the campaigns head north to Michigan, Illinois and Ohio in the next 10 days.
5. Rubio and Kasich can't wait to go home
While Trump and Cruz both claimed victories Saturday, Rubio and Kasich, the governor of Ohio, played only a minor role in the four states that participated.
Both are relying heavily on upcoming contests in their home states -- Rubio in Florida and Kasich in Ohio -- on March 15. If they don't win at home, it's hard to see how either proceeds in this race.
Florida and Ohio are both big, winner-take-all states, so victories in both of those states would make it more difficult for Trump to secure the delegates he needs to clinch the nomination.
But Saturday's results certainly don't give either of them increased momentum going into their March 15 home-field contests. And to the extent that Rubio's harsh attacks on Trump last week, particularly at the Fox News debate on Thursday night, played into Saturday's results, they seemed to have helped Cruz more than anyone.
Rubio downplayed the Saturday results during a press conference in Puerto Rico, where he is making a play for the U.S. territory's 23 delegates, to be doled out Sunday.
"There will be more delegates awarded in Florida than basically any other state that voted tonight combined," Rubio said. "There are clearly states in which some of my opponents do better than us because it fits the profile they've targeted. We understood that."
Rubio's campaign pointed to upcoming states on the electoral calendar, particularly the fact that there are only two states left that hold caucuses. His team believes he will do better in primaries, though so far he has only won one contest -- in Minnesota -- which was a caucus.
But primaries are also likely to benefit Trump, which has been more successful under that system than caucuses.