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Former U.S. Secretary of State Hillary Clinton and U.S. Sen. Bernie Sanders of Vermont stand together before the start of a debate in South Carolina on Jan. 17. Both are competing to win Ohio's Democratic presidential primary on Tuesday.

(Mic Smith, Associated Press)

COLUMBUS, Ohio--Conventional wisdom holds that Hillary Clinton will win Ohio's Democratic presidential primary on Tuesday.

But so far, this has not been a conventional year.

Several political analysts and insiders said they expect Clinton to win Ohio on March 15, given her win in the 2008 Democratic primary here and polls showing her leading Bernie Sanders.

But Sanders is surging, most recently with a surprise victory in Michigan last week.

And recent polls in Ohio have been all over the place, showing Clinton's lead everywhere from 30 percent (last week) to 5 percent (Monday).

"Clinton is likely going to take Ohio, but the margin is going to be smaller than what we expected," said Thomas Sutton, who chairs the political science department at Baldwin Wallace University.

No matter who wins Ohio, the loser could still capture a large amount of presidential delegates from the state, as delegates are awarded proportionally.

Here are five factors we're watching for Tuesday's Ohio Democratic presidential primary:

Areas of Northeast Ohio and Columbus will be particularly important: Democrats in parts of Northeast Ohio and the Columbus area will have a disproportionate impact on who wins Ohio's Democratic primary.

Here's why: unlike the Republicans, Ohio Democrats don't award all of their 143 elected Democratic delegates to the candidate who gets the most votes statewide.

Rather, Democrats pick their delegates in two ways: 50 delegates will be awarded proportionally based on the statewide vote total, while the other 93 will be elected based on proportional vote totals in each of the state's 16 congressional districts.

Ohio's four congressional districts held by a Democrat elect far more delegates than the 12 held by Republicans. Those four districts (two in Greater Cleveland, one in the Youngstown area, and one in the Columbus region) will choose a total of 45 delegates - more than 30 percent of the state's total elected delegate total.

Such a system may work in Clinton's favor. In Ohio's 11th congressional district, which includes a large part of Cleveland and Akron and elects 17 delegates by itself, 54 percent of the population is black. Ohio's 3rd congressional district, which covers much of Columbus, is about one-third black.

In addition, three of Ohio's four Democratic districts are represented by Clinton supporters: U.S. Reps. Joyce Beatty, Marcia Fudge, and Tim Ryan. The fourth, U.S. Rep. Marcy Kaptur, endorsed Sanders last Friday.

Hillary is relying on the urban vote: Clinton's key bases of support in Ohio are in the state's largest cities, including Cincinnati, Cleveland, Columbus, and Toledo. In particular, she's expecting significant support from black voters, a demographic that has consistently backed her by wide margins in other early primary states.

Clinton's starting point will, ironically, be the five counties she lost in the 2008 Democratic primary: Cuyahoga (Cleveland), Delaware (north of Columbus), Franklin (Columbus), Hamilton (Cincinnati), and Montgomery (Dayton).

"In some ways, Clinton has kind of picked up the old Obama vote, obviously among African-Americans, because African-Americans were strong for Obama last time, and now they're strongly for Clinton," said Kyle Kondik, managing editor of Sabato's Crystal Ball, the University of Virginia Center for Politics' nonpartisan political newsletter.

"I think you look at maybe those five counties as Clinton's starting point, and we'll see how much she builds off from that."

Clinton's campaign has been reaching out to rural areas as well - last week, Bill Clinton made a point of campaigning for his wife in Chillicothe as well as Columbus and Dayton.

And there's a gender gap: an Ohio poll released Monday found that women back Clinton over Sanders 56 percent to 39 percent, while men preferred Sanders 55 percent to 43 percent.

In summary, Clinton will be in good shape if she can turn out large numbers of Democrats from the "three Cs" - Columbus, Cincinnati, and Cleveland - while staying competitive in other areas of the state.

"If the African-American vote is high, that is very likely to benefit Hillary Clinton," said University of Akron political scientist John Green.

Bernie needs a boost from young voters, 'Reagan Democrats': Sanders, meanwhile, doesn't have a geographic base of support, though he'll likely do well in rural areas and in college towns.

To win, though, Sanders needs a strong turnout from an unlikely group of voters: blue-collar white males, previously known as "Reagan Democrats." These are voters who often live in small to mid-sized towns, have often lost their manufacturing jobs or work part-time, and have lost faith in establishment politicians.

What's unclear, Sutton said, is whether these Democratic voters will vote in greater numbers than they have in the past, and, if so, whether they'll vote for Sanders or - surprisingly - Republican Donald Trump, another outsider candidate who's capitalizing on widespread disillusionment with the U.S. political system. There have already been indications that many Ohio Democrats are planning to back Trump.

Bernie's spring break problem: Sanders has dominated among younger voters in other states, and he'll need a strong show of support from them in Ohio on Tuesday.

However, Sanders could face a problem: about 167,000 of Ohio's roughly 575,000 college students will be on spring break on election day - including students at Ohio State University, Cleveland State University, and Cuyahoga Community College.

Sanders' campaign has worked to have student supporters vote absentee, but that can be inconvenient - as Politico noted, the closest early-voting center to Ohio State is 15 minutes away by car and 40 minutes away by bus.

Experts are split on the importance of so many students being away from campus.

Most students at those schools are from Ohio, so many of them will still vote from their hometowns, Kondik said.

But Sutton noted that others will be on vacation on Florida, Mexico, or other places, and even in-state students will be dispersed and harder for Sanders' campaign to reach and mobilize.

"It'll make a huge difference," Sutton said.

Both campaigns haven't had much time to organize: Back in 2008, the Clinton and Obama campaigns both had several weeks or so to build strong organizations leading up to the primary election.

But this year's primary calendar has been accelerated, forcing both the Clinton and Sanders campaigns to create statewide organizations in a hurry. Neither campaign opened an official field office in the Buckeye State until late February, and Clinton and Sanders have only ramped up their appearances in the state during in the past week.

"I remember when I was here eight years ago, I made 21 [campaign] stops," Bill Clinton told a group of supporters in Columbus last week. Before then, he had only held one public event in Ohio this election season. "So we have to depend on you."