Donald Trump and Hillary Clinton currently lead the delegate counts for the presidential nomination. But because of the difference in how both parties award their delegates, Clinton's is the more commanding lead.

Michigan is an important test for Sanders

Tuesday's Democratic contest in Michigan, the biggest prize of the day, is key for Bernie Sanders to show he can turn things around. His campaign has argued that Clinton has ballooned her lead because of black voters in the South.

Now, many of those Southern contests are over (though there is another Tuesday in Mississippi).

But the question remains: Can the Vermont independent senator appeal to Northern black voters? They make up roughly a quarter of Michigan's Democratic electorate. He believes his economic message can resonate with them and working-class whites hurt by trade. Polls, though, have shown the former secretary of state with double-digit leads going into Tuesday.

Sanders is facing a difficult problem: This past weekend, he won three of four contests, but, because his wins were in smaller caucuses, and Clinton won by a huge margin in the primary in Louisiana, Sanders only wound up winning three more pledged delegates than Clinton. (Pledged delegates are derived from the margins candidates win in voting in various state primaries and caucuses.)

Maintaining that kind of pace will not help Sanders catch Clinton, who is 195 delegates ahead. Sanders needs 53 percent of all remaining delegates to win a majority of pledged delegates. And with each passing contest, that hill becomes even steeper. With superdelegates, those unpledged party leaders and elected officials, factored in, Sanders needs a whopping 60 percent of all remaining delegates. That's a very difficult aircraft carrier to turn around, given the Democrats' proportional system of allocating delegates.

Hillary Clinton speaks at the Charles H. Wright Museum of African American History in Detroit. She again hopes black support pushes her over the top in Michigan. (Charlie Neibergall/AP)

Yes, superdelegates can change their votes, and it's true they have never not gone with who won the pledged majority, but even in 2008, when Barack Obama defeated Clinton, and won more superdelegates, not all that many superdelegates peeled off from Clinton. What's more, Clinton has a far bigger lead with them now than she ever did in 2008. Clinton already has nearly two-thirds of all superdelegates publicly in her corner. (And, by the way, they were created in the 1980s for precisely this purpose — to give party leaders a lever to prevent the nomination of what they view as an unelectable candidate after Democrats were soundly defeated in 1984.)

All that said, the pledged-delegate margin remains the most important number to watch. Clinton would prefer to win the nomination outright based on voting — and not because party leaders put her over the top. There's lots of talk of the GOP civil war, but if there was an outcome in which one candidate won the delegates from actual voters and the other won the nomination because of party insiders, you can bet there would be an equally ugly Democratic convention in Philadelphia this summer.

But unless Sanders starts winning soon and big, that's all theoretical and moot. The Democratic race, at this point, doesn't look close to heading toward anything like that.

Pressure is on Trump to regain the "inevitable" narrative

Donald Trump speaks during a rally at Macomb Community College in Michigan. (Scott Olson/Getty Images)

For Republicans, though, Trump is ahead, his lead is less dominant because it's a four-person race — and the candidates keep splitting the vote.

On Tuesday, Michigan has the most delegates in play with 59, far less than on the Democratic side, in part because Republicans have far fewer delegates overall, but also because of the state's history of voting Democratic.

Trump has been leading the polls there by double digits, and he needs another big win. The other contests of the day, though — in Mississippi, Idaho and Hawaii — hold far more delegates combined (91) than Michigan. There hasn't been any good polling in Mississippi, but Trump hopes to pull off a win there like he did in neighboring Louisiana over the weekend. If Louisiana is an indicator, though, Cruz could give Trump a run for his money.

If Cruz pulled that off, it would be yet another example that he could use to say he's the principal alternative to Trump — and not Marco Rubio. This past weekend, Cruz, who trails Trump by 84 delegates, made a strong case for that. He won the biggest share of the delegates out of a handful of contests with wins in Kansas and Maine — and he nearly picked off Trump in Louisiana and Kentucky.

Rubio finished third everywhere on Saturday, except in Maine, where he finished fourth. He made up for it some in Puerto Rico on Sunday, winning there by such a big margin that he took all of the territory's 23 delegates.

The GOP political establishment couldn't think of a worse possible choice than having to pick between Trump and Cruz, who might be the least liked person in Congress among his colleagues.

And then there's John Kasich. The Ohio governor is hoping to surprise the field in Michigan. He should do well there. He's a Midwesterner. But he's polling double digits behind Trump, and some polls have had Cruz either in second or a close third. If Kasich is far behind in Michigan or even finishes third behind Cruz, it's hard for him to make a case that he has a real chance at the nomination.

He'll likely stay in for the winner-take-all March 15 contest in his home state of Ohio, but what's his sell for staying in after that — aside from maybe trying to keep Trump below a majority heading into the convention by picking off votes and delegates where he can in more moderate places?

Because of the crowded field, unlike the two-person race on the Democratic side, Trump currently still needs 53 percent of all remaining delegates to win the nomination. But he has only won the majority of delegates in five of 20 states so far.

That's not to say anyone else on the GOP side has a better chance of winning a majority — Cruz needs 59 percent of all remaining delegates, Rubio 68 percent and Kasich 75 percent.

The candidates hope to start racking up more lopsided wins, as the contest rules change on March 15. That's when states can pick however they want to award delegates. Some states, like Florida, Ohio, Arizona and New Jersey, are winner take all; others are more hybrid. All of that is to say there could be some funky results, spikes and dips ahead that could sway the race in a potentially unknown direction.

But clearly, at this point, Trump is in the driver's seat. He has solid support with his hardened base that will get him a lot of delegates before June when the contests are eventually over. The question that still remains for him is: Will he grow his support?

Through 20 contests, he has averaged 35 percent of the vote. He's cracked 40 percent in five states so far and 50 percent in just one (New Hampshire). That's why he's been publicly calling for candidates, like Rubio, to get out of the race.

The theory of the establishment coalescing behind a single candidate to beat Trump might not hold true, but what might be true is Trump needs the field to shrink to get a majority before the convention.

Here's what you need to know for Tuesday's races

By Barbara Sprunt and Domenico Montanaro

How many states vote? Four: Hawaii, Idaho, Michigan and Mississippi. (All four vote on the GOP side, but just Michigan and Mississippi vote on the Democratic side.)

When do polls close? 8 p.m. ET (Mississippi), 9 p.m. ET (Michigan — most polls close at 8 p.m. ET, but some counties are in Central), 11 p.m. ET (Idaho), 1 a.m. ET (Hawaii).

How many delegates are at stake? 316 combined (338 if 22 Democratic superdelegates are included):

-- 188 Democrats (Michigan: 130 pledged+17 supers; Mississippi: 36 pledged+5 supers)

— 150 Republican (Michigan: 59; Mississippi: 40; Idaho: 32; Hawaii: 19)

Remind me what happened on Super Tuesday? Trump won big, picking up victories in Alabama, Arkansas, Georgia, Massachusetts, Tennessee, Vermont and Virginia. Cruz won his home state of Texas and also Oklahoma and Alaska. Marco Rubio eked out his first victory — in the Minnesota caucuses. That was enough to guarantee that both senators would be in the race until at least March 15, when more states become winner-take-all, including Rubio's must-win home state of Florida.

For the Democrats, Clinton won Alabama, Arkansas, Georgia, Massachusetts, Tennessee, Texas and Virginia. Sanders won Colorado, Minnesota, Oklahoma and his home state of Vermont.

Did anything happen after Super Tuesday? Yes. On the Democratic side, Sanders won the caucuses in Maine, Kansas and Nebraska. Clinton won by a huge margin in the Louisiana primary.

On the GOP side, Cruz won the most delegates out of this past weekend with wins in Kansas and Maine on Saturday. Trump pulled off narrow victories in Louisiana and Kentucky. Rubio won the Republican primary in Puerto Rico on Sunday by more than 50 percent of the vote, giving him all 23 delegates (which, by the way, is as many delegates as in New Hampshire).

What is the current delegate count? On the GOP side, Trump has 384 delegates. In second place is Cruz with 300. Rubio has 151 and Kasich 37. Remember, the Republicans need 1,237 delegates to get the nomination.

On the Democratic side, Clinton leads with pledged delegates 672 to 477 for Sanders. With superdelegates factored in (458 for Clinton), her total balloons to 1,130 to Sanders' 499 (with just 22 superdelegates).

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