'Super Tuesday: the sequel' guide: What to watch for in 5 states

By the time polls close Tuesday, the Republican presidential race may be a 3- or even 2-man race. That's because Tuesday's contests in five states represent a last chance for Sen. Marco Rubio and Gov. John Kasich – and possibly the last chance for the GOP to stop Donald Trump's march to the party's presidential nomination.

On the GOP side, all eyes will be on the delegate-rich, winner-take-all states of Florida (99 delegates) and Ohio (66 delegates), on which Sen. Rubio and Gov. Kasich are staking their campaigns. Also voting are Illinois, Missouri, and North Carolina.

On the Democratic side, Tuesday's results will determine whether Hillary Clinton can clinch the nomination quickly, or whether Sen. Bernie Sanders's surprising staying power will continue.

Here's what to watch for Tuesday:

Marco Rubio: After a series of disappointing losses, the senator from Florida has been staking his entire candidacy on a victory in his home state, which awards the GOP winner all 99 of its delegates. A loss in Florida would probably force the candidate out of the race, crushing Rubio's presidential aspirations for 2016. Unfortunately for Rubio, the polls don't look good. A Quinnipiac poll released Monday shows Rubio trailing Trump by 24 points in Florida. And a Marist/NBC/Wall Street Journal poll shows Trump leading Rubio in the Sunshine State, 43 percent to 22 percent. In fact, as forecasting blog FiveThirtyEight pointed out, Trump has led every single poll taken there this year.

To some degree, Rubio's entire political career is at stake today in Florida.

"A loss of that magnitude could be devastating to Rubio, and leave him in a tough spot if he ever wanted to seek public office again," reports CNN.

John Kasich: Though the Ohio governor's situation is less dire then Rubio's, he also has justified staying in the race by pointing to his own home state. As such, a victory in this winner-take-all contest is essential for Kasich. The polls look better for the Ohio governor, whom former House Speaker John Boehner recently endorsed. A Marist survey shows Kasich holding the edge in the Buckeye State with 39 percent to Trump’s 33 percent. But a Quinnipiac poll shows Trump and Kasich tied in Ohio, with 38 percent each.

Though Kasich initially said he'll drop out of the race if he doesn't win Ohio, more recently he's backed off that promise.

Ted Cruz: The Texas senator has two goals going into Tuesday's contests: Vacuum up a lot of delegates without winning a single state, and drive Rubio and Kasich out of the race.

“It will be absolutely clear to everyone that this is a two-man race,” Sen. Cruz said told reporters Monday in Peoria, Illinois. “I think after tomorrow it will be officially a two-man race. Because no other candidate has any plausible path to 1,237.”

Cruz has 370 delegates so far, the second-highest count in the GOP field, and he wants to add many of the 358 delegates at stake Tuesday. He hopes a strong delegate count, along with Republicans' growing wariness of Trump, at whose rallies violence erupted this past weekend, will rally the party to his cause.

Donald Trump: Tuesday's delegate-rich races give the billionaire candidate an opportunity to nail down the nomination. With 469 delegates, he leads the GOP numbers race. If he sweeps most or all of the states voting Tuesday, he still won't achieve the 1,237 needed to win the nomination, but he'll make it nearly impossible for any other candidate to amass enough delegates to win.

A few twists: Rubio’s communications director recently told Rubio supporters to vote for Kasich in Ohio to stop Trump. And Trump is unlikely to reach a majority of delegates needed to clinch the Republican nomination if he loses Ohio, notes FiveThirtyEight's Harry Enten.

Violence broke out at several Trump rallies this past weekend, and Trump initially appeared to defend supporters who threw punches, promising to pay for their legal fees. The incidents put him on the defensive, and has party leaders increasingly wary.

As rival Cruz said on ABC’s “This Week," a Trump nomination would be “a disaster for Republicans, for conservatives. I think it’s a disaster for the country because if Donald is the nominee, it makes it much, much more likely that Hillary Clinton wins the general.”

How the violent incidents affect Trump's performance Tuesday remains to be seen. 

Hillary Clinton: Mrs. Clinton, who leads Senator Sanders by 214 pledged delegates, was hoping to clinch the nomination after last week's contests. But a surprise Sanders' upset in Michigan presented a detour on her road to the nomination. Tuesday's results may determine whether Clinton's camp can regain momentum and shift their focus to the general election – or not.

So far, the polls suggest Clinton is well-positioned to win in important states like Florida, where she leads Sanders 62 percent to 34 percent, according to a CBS poll, and Ohio, where she leads him 52 percent to 43 percent. But Sanders has a narrow 48 percent to 46 percent lead in Illinois. If he beats Clinton here and elsewhere, he may make the nominating race a longer slog, forcing his rival to spend more time and money in the nominating race rather than the general election.

Bernie Sanders: While Clinton is trying to prove Michigan was an anomaly, Sanders is trying to prove the opposite: that he's not simply a regional candidate and that his economic message resonates in midwestern Rust Belt states such as Michigan, Illinois, Ohio, and Missouri. As such, he's been doubling down on his attacks that Clinton's support for international trade agreements destroyed jobs in the US. If his attacks work, he may rack up more wins and delegates, giving him added momentum as the race moves to friendlier territory out west, and proving he's still a viable contender. If not, he may face increased pressure from party officials who say he's weakening Clinton for the general election, to drop out.