Demographic groups in both parties have shown stark divides this primary season. Age, race and location have each played outsized roles in determining the GOP and Democratic frontrunners. And judging from this year's past contests, here's a look at the key voting blocs and areas to watch for to see who will come out on top in Tuesday's primaries:
Trump's Potential Wins: Michigan (59 delegates) and Mississippi (40 delegates)
Donald Trump has dominated in the South and leads in most polls in Michigan. So he is the favorite to win the two most delegate-rich states on Tuesday.
Generally, Trump is very strong among white voters without college degrees, making Mississippi an ideal state for him. About 20 percent of its residents over age 25 have bachelor's degrees, compared to about 29 percent nationally.
But Saturday's primary in Louisiana suggests Texas Sen. Ted Cruz could be a threat to Trump in Mississippi.
Cruz carried a bloc of counties in rural, northeastern Louisiana that have relatively few people with bachelor's degrees and high black populations, the kinds of places where Trump generally dominates.
That made Louisiana's results much closer than expected, since Trump had easily won primaries in Alabama and Georgia a few days earlier.
What changed? After Super Tuesday, Mitt Romney blasted Trump and urged Republicans not to vote for him. And the mogul made some bizarre comments during a GOP debate.
But the most important factors may have been Marco Rubio and Ben Carson.
In Alabama, which voted on Super Tuesday, Trump won 43 percent of the vote. Rubio and Carson combined for 29 percent, helping split the anti-Trump vote.
On Saturday in Louisiana, Trump won 41 percent, similar to his showing in Alabama. But Carson, who had announced he was ending his campaign on Friday, and Rubio combined for only 13 percent.
Cruz seems to have won the plurality of these non-Trump voters in Louisiana, getting to 38 percent overall.
While Cruz is the obvious Trump alternative in Mississippi, none of the states that have voted so far are analogous to Michigan. It's more racially-diverse than nearby Iowa or Minnesota. And it's holding a primary, while Iowa and Minnesota held caucuses, which tend to depress Trump's support.
There are plenty of white, working-class voters in Michigan, so Trump will have a strong base there.
But the upper-income counties around Detroit could prove resistant to Trump. For example, in Oakland County, near Detroit, the more establishment Republican Romney won 50 percent of the vote in 2012. That is fertile ground for Trump's opponents.
So far in the primary process, Republicans in urban, upper-income counties have often preferred other candidates to Trump. But they have not coalesced around a single person.
The Republicans in Northern Virginia near Washington, D.C. backed Rubio, those in Burlington, Vermont liked Ohio Gov. John Kasich, while Republicans in and around Birmingham, Alabama, Little Rock, Arkansas and Louisville, Kentucky were about equally split between Cruz and Rubio.
Some polls in Michigan show Kasich surging. And there is potential for college-educated, upper-income voters in Michigan to unify behind the Ohio governor. Cruz may be too conservative and evangelical for these voters, while Rubio, after his dismal showings in recent primaries, is in danger of appearing to be a candidate with no chance of winning the nomination.
Kasich is well-positioned for a second-place finish in Michigan, but a victory would still be a major upset. Rubio and Cruz are likely to get chunks of the college-educated GOP vote, eating into Kasich's potential support.
Trump Potential Losses: Idaho (32) and Hawaii (19)
Cruz seems to be the strongest candidate in lightly-populated states (Alaska, Maine) and caucuses (Alaska, Maine, Iowa, Kansas). This suggests he has deep support among the most committed Republican activists and a formidable on-the-ground campaign operation.
Hawaii is holding caucuses, and while Idaho has a primary, the contest will still likely have fewer than 100,000 voters.
But Hawaii and Idaho both are demographic outliers in ways that make it difficult to predict the winners. Idaho's population is about 25 percent Mormon, a potential barrier for the Southern Baptist Cruz and therefore an advantage for Trump. There are more Asians (38 percent) than whites (23 percent) in Hawaii.
For Clinton, Potential For Two Blowouts
Mississippi's Democratic electorate is about half African-American. If the pattern from other states continues there, Clinton would carry more than 80 percent of the black vote. Because of that huge deficit among Africans-Americans, Sanders could fall below even 35 percent of the overall vote in Mississippi, continuing his series of resounding defeats to Clinton in the South.
The data on Michigan is less clear. In 2008, because of an internal Democratic Party dispute, Clinton competed in the state but Barack Obama did not.
Even without Obama's campaign organizing in the state, 23 percent of the electorate was black in 2008. That number could be higher in Tuesday's primary, a challenge for Sanders.
Michigan will be a revealing contest in the Democratic race. Demographics have predicted many of the early primaries and caucuses, as states with large black populations went to Clinton, while Sanders carried those with very small black populations.
If Michigan's electorate is between 25 and 33 percent black, as expected, that is closer to the median of the Democratic Party overall. And Sanders' core message -- that the American middle class is eroding and that jobs in fields like manufacturing are vital to reversing that trend—is well-suited to states like Michigan and Wisconsin.
Even if Clinton wins the overwhelming majority of the black vote in Michigan, Sanders could carry the state if he gets large margins of the Democrats outside of the Detroit area, which is heavily African-American.
The map of a Sanders win in Michigan would resemble that of Trump in some ways: overwhelming strength in rural areas, minimizing losses around Detroit.
Sanders also needs do well in the Ann Arbor area around the University of Michigan, which has lots of liberals under age 45, the kind of voters who tend to back the Vermont senator.