Michigan's voters breathed new life into Bernie Sanders's campaign last week by handing the Vermont senator one of the biggest upsets in recent presidential primary history.

Sanders's win in Michigan didn't just prove that he could have a shot in other big Midwestern states like Ohio and Illinois, which are holding their primaries today; it also helps him tell a better story about how he wins the nomination.

And that story itself really does matter. The perceived state of the race has an impact on how voters behave, even though it has no relationship to a candidate's positions or policies.

"There is such a thing as momentum. Altering perceptions of electability among voters can really be persuasive," said Adam Seth Levine, a political scientist at Cornell University.

Of course, Clinton remains the clear frontrunner. Sanders trails by more than 200 pledged delegates and has received just 3.3 million votes to the 4.9 million received by Clinton since the Iowa caucuses on February 1.

Will Michigan help swing the pendulum in his direction? With voters in five states headed to the ballot box on Tuesday, we'll get several excellent opportunities to find out.

What to look for, state by state, on "Super Tuesday II"

There are five states voting today — North Carolina, Missouri, Ohio, Florida, and Illinois. Here's a shorthand way to quickly evaluate how to interpret the returns as they come in:

Illinois is the most important contest to watch today. Clinton has led in most of the polling there, but there’s at least a chance that the state might deliver Sanders a dramatic, race-altering upset — though if the victory is narrow, he won't gain much ground in delegates.

In Missouri and Ohio, Sanders probably needs to win to maintain a plausible path to the nomination. If he doesn't, he'll only be falling further behind Clinton in delegates at a time when he really needs to start catching up.

In both North Carolina and Florida, Clinton is more heavily favored to win, since these states have demographics that more closely match the states in which she's performed best. But what's really important here are the margins. The bigger Clinton's wins are here, the more her delegate lead over Sanders will likely expand.

Illinois: the real test of whether Sanders can carve into Clinton's core support

Of the five states voting on Tuesday, Illinois has the most potential to dramatically transform what we know about the campaign.

Sanders could lose in Florida and North Carolina and still feel good about his path to the nomination. Clinton could lose in Missouri and Ohio and wake up on Wednesday about as confident as she was the day before.

Illinois is different. A come-from-behind win for Sanders there would really tell us something new about his strength, much as Michigan was the first sign of Sanders's appeal in the Rust Belt.

"If Sanders wins Illinois, we're in a new race," said Richard Berg-Andersson, who tracks delegate math at the Green Papers. "Wow, that would be a big story."

Of course, a Sanders upset in North Carolina or Florida — where Clinton has dominated the polls — would be dramatic as well.

But it's worth focusing on Illinois, because that's where it looks like Sanders may actually have a real shot. One CBS poll put him up by 2 points this week, and Politico reports that he's been savvily turning the race into something of a referendum on Chicago Mayor (and Clinton ally) Rahm Emanuel.

A loss in Illinois would weaken Clinton's frontrunner status for other reasons as well. The state will likely have the most black voters of the five states voting today, Clinton was raised in the suburbs of Chicago, and downstate Illinois looks much like Clinton's stronghold in the South, according to Berg-Andersson.

Close trackers of the race have long assumed that Clinton's delegate lead would be buttressed by big Northeastern states with diverse populations and powerful Democratic establishments — New York, Pennsylvania, New Jersey. If she loses in Illinois, those major contests will suddenly appear up for grabs.

Missouri, Ohio: two states with heavily white electorates; Sanders will likely need both to be the nominee

Clinton has only won two states this election where white voters made up at least 70 percent of the electorate, and she only won them by razor-thin margins. (She took Iowa 49.9 to 49.6 and Massachusetts 50.1 to 48.7.)

If Sanders's dominance among white voters continues, he's probably most likely to win today in Ohio (where 76 percent of primary voters were white in 2008) and in Missouri (where 80 percent were white).

Though Sanders has trailed by double digits in some polls, Ohio may be fertile ground for him in part because his populist pitch on trade may resonate for the same reasons it did in Michigan, Berg-Andersson says.

"Everyone forgets: Ohio has almost as much auto economics as Michigan," Berg-Andersson said. "Ohio is very much like Michigan: He should be competitive there, if not win outright."

Missouri is tough to game out, in part because there's been very little polling to come out of the state.

The state's heavily white electorate is one reason to think Sanders will have an advantage. But it's not clear if white Missouri Democrats will vote like their western neighbors in Oklahoma and Nebraska (which supported Sanders), or like their eastern neighbors in Tennessee (which supported Clinton).

North Carolina, Florida: Clinton should hold these states easily

As two Southern states with diverse Democratic primary electorates, Florida and North Carolina should be right in Clinton's wheelhouse.

Florida is the biggest prize of all Super Tuesday II states. It should be favorable terrain for Clinton for several reasons:

African Americans and Latinos will make up a substantial portion of the electorate.

The white voters that are in Florida tend to be older, and older voters have broken by huge margins for Clinton. (In 2008, about 40 percent of Democratic primary voters in Florida were over 65; in Michigan last week, fewer than 20 percent fit in the oldest age category).

The state has a closed primary, meaning independents — who have overwhelmingly supported Sanders when allowed to — will not be a factor.

Florida still looks much more like the South than many realize. "The further north you go, the more Southern it gets in Florida," Berg-Andersson said. "That will help Hillary."

Many of the same factors apply in North Carolina. Though there are some college towns in the state, it's hard to imagine Sanders will win there given his landslide loss in neighboring Virginia on Super Tuesday.

"I think Hillary will definitely win Florida and definitely North Carolina," said Seth McKee, a professor of political science at Texas Tech.

Still, it's important to remember here that Sanders can't afford to get blown out if he's only squeaking out victories elsewhere. Delegates in the Democratic primary are awarded proportionally, so it's important for Sanders to at least keep it close in these states if he's going to maintain a case for how he wins the nomination.

Where the map goes from here

The problem for Sanders is that even if he has a much better than expected Super Tuesday II — wins in Ohio, Illinois, and Missouri and narrow defeats in North Carolina and Florida — it's unlikely to change the fundamental delegate math.

"Winning by a small margin isn't going to be enough for Bernie. He needs decisive victories," says Matthew Dickinson, a political science professor at Middlebury College, in an email.

The good news for Sanders's campaign is that there's still time. If he manages to rack up landslides in heavily white states like Wisconsin and Indiana, and get the upper hand over Clinton in those big Northeastern states and California, he could still mount a comeback.

But McKee doesn't think Sanders's fans should be optimistic. "Obama never had a huge lead over Hillary, but he built it over the early seven states and kept it," he said of the 2008 Democratic primary. "Hillary has done the same thing — except her lead is larger than Obama's was."