Editor's Note: (Julian Zelizer is a professor of history and public affairs at Princeton University and a New America fellow. He is the author of "Jimmy Carter" and "The Fierce Urgency of Now: Lyndon Johnson, Congress, and the Battle for the Great Society." The opinions expressed in this commentary are his.)
(CNN) This Tuesday is poised to be the most significant night since Super Tuesday on March 1 in shaping the dynamics of the presidential race for both parties.
Indeed, with fewer candidates in the competition, and with each candidate having demonstrated more of their electoral chops, the outcome in the winner-take-all states of Florida and Ohio could potentially have a major impact on what will happen in the weeks leading up to the convention.
Here are the four key questions that Tuesday night's contests in Florida, Illinois, Missouri, North Carolina, Northern Mariana Islands and Ohio will answer:
1. Can Donald Trump and Ted Cruz squeeze Marco Rubio in Florida?
With Cruz having focused some of his energy on campaigning in Florida with the goal of knocking out Rubio, the most formidable "establishment" candidate in the bunch, Trump has a very good opportunity to take this delegate pool.
He remains ahead in the polls. A defeat for Rubio in his home state of Florida would kill his campaign, an outcome that would also be good for Cruz, who would probably pick up much of Rubio's support.
2. Can Donald Trump prove his coalition claim?
Throughout the past few weeks, Trump has been pushing back against Cruz supporters by saying that he is the only candidate of the two who would do well in the general election. Unlike the solidly right-wing Cruz, Trump argues, only he could attract a diverse political coalition and win in Northern states. In Michigan, Trump has provided some proof to support his claim, but Ohio and Florida would be the most powerful evidence.
If Trump can win by significant margins in these swing states, that will be crucial to the general election and he'll have some rather significant data to back up his major argument.
In addition, he would be one of only three Republicans in recent decades to sweep the Deep South in the middle of a contested primary (George W. Bush and Ronald Reagan being the other two to do so). The anti-Trump coalition within the GOP, meanwhile, would have a much more difficult time building support for any remaining establishment candidate such as John Kasich or even Cruz.
One outstanding question on Tuesday is how the violence and chaos that unfolded this weekend affects voter perceptions of the front-runner. Do they play into the anti-Trump arguments that his candidacy is dangerous, racist and illegitimate? Or do they fuel his narrative, and that of his supporters, of an embattled insurgent fighting tooth and nail to challenge powerful political actors who are willing to do anything necessary to stop him?
3. Does Kasich become the last establishment candidate standing?
This is an important moment for Kasich, who has been betting the farm on the fact that he can win in Ohio, where he has been an enormously popular governor. The problem is that Ohio has been leaning toward Trump.
Still, this is a state where Kasich can really show some muscle, and if he can pull out a victory, and if Rubio loses in Florida, he would emerge as the strongest non-Cruz candidate to challenge Trump. And with a victory in this key swing state, where economic concerns loom large, he could be the person best positioned in a brokered convention to take the nomination from Trump.
On the other hand, if he loses in Ohio, it would be devastating to his chances for remaining viable in the campaign.
4. How much is economic unrest going to upset Hillary Clinton in a general election?
Even with all of his success so far, Bernie Sanders' ability to win a general election remains unclear to say the least. But with a number of important primary victories -- Michigan, Kansas, Maine -- the odds have gotten better that he will be able to continue his campaign deep into the primary season and remain a vital force in the convention.
While it is true that Sanders is essentially a one-issue candidate, the fact is that economics is a huge and defining issue that cuts across all segments of the electorate, with many expressing deep concern about their economic prospects. Meanwhile, one of the most notable outcomes of Michigan was that Clinton did not do nearly as well with African American voters as expected, suggesting that they, like many white Americans, are frustrated and fearful about their situation.
Even assuming Clinton wins the nomination, Sanders' success has underscored how deeply insecure about the future many Americans are feeling, including in states where she would be expected to do well as a Democrat as well as some swing states.
Clearly, many voters are not especially enthused by the solutions she is proposing to the problems they face. With this in mind, Trump's anti-establishment message and brand could prove attractive to many voters. Plus, there is also the significant possibility that dampened voter enthusiasm in the primaries for Democrats will roll over into the presidential race, while Trump will be able to energize his supporters to turn out.
Of course, if Clinton can win Florida and Ohio, she would deliver a devastating blow to the Sanders campaign. Yes, he could certainly keep going, but she would undoubtedly have the momentum she needs to significantly boost her chances in Northern states.
Whatever happens Tuesday, it will be a big day for both parties and their candidates. And, with voters in these extremely important swing states making some key decisions on who should and should not have a path to victory, the likely front-runner for each party should become much clearer by the time the polls close.
Join us on Facebook.com/CNNOpinion.
Read CNNOpinion's Flipboard magazine.