Perhaps more than for any other state, the road to the White House runs through Ohio. That is particularly true for Mitt Romney, whose continual campaigning there has suggested he is keenly aware of the fact that no Republican candidate has won the presidency without also capturing the Buckeye State. Romney can lose Ohio and still win the election, but his path to do so would narrow significantly.

The Obama campaign is hoping that its formidable get-out-the-vote operation, built on the framework erected in 2008, can play a pivotal role in boosting turnout. The campaign has also pushed hard to keep early voting in place, winning a legal battle by preventing Ohio from curtailing early voting.

For his part, Romney is hoping that financially struggling Ohio residents, particularly working-class whites, will be drawn to his message of economic revitalization. That could be a tough balance to strike, with Ohio’s economy doing comparatively better than the country’s -- its September unemployment rate was 7 percent, down from 7.4 percent in April, compared to 7.9 percent nationwide in October -- and with Obama touting his auto bailout.

To get a sense of which way Ohio is breaking, it’s helpful to take a look at past elections. As with most states, Ohio has a handful of more populous counties that tend to break Democratic and a proliferation of smaller counties that are more likely to go Republican.

Joan McLean, a professor of political science at Ohio Wesleyan University, drew a parallel to the 2010 gubernatorial race, when Republican John Kasich edged out Democrat Ted Strickland in one of Ohio’s closest races in decades. Strickland ran up a 120,000-vote advantage in the state’s nine largest counties, McLean noted, but Kasich counteracted that with a 217,000-vote margin of victory in the other 79 counties.

Obama needs to perform as well as Strickland did in Montgomery and Hamilton counties, McLean said (Hamilton is a big prize -- after backing George W. Bush narrowly in 2000 and then more convincingly in 2004, the county chose Obama over John McCain by some 30,000 votes). On top of that, she said, Obama needs to outperform Strickland in Cuyahoga, Franklin, Summit, Lucas, Stark, Butler and Lorain counties. Obama won all but Butler in 2008, running up huge margins in Cuyahoga, which encompasses the Cleveland metro area, and Franklin, home to Columbus.

“Race will be about turnout in these areas,” McLean wrote in an email. “Romney appears to have the base Kasich turned out to beat Strickland in 2010 ... so Dems won't be taking those votes away, but they must increase their turnout and margin of victory in these larger, more Democratic counties.”

States award electoral votes on a winner-take-all basis, so focusing on county results can be misleading. Daniel Coffey, a professor of political science at the University of Akron, said that narrow county results are more a result of turnout than of voters shifting party allegiances and said it is more instructive to look at broad regions instead. President Obama is expected to perform well in the northeastern part of the state, which contains cities like Cleveland, Akron and Youngstown; the southeast has traditionally been a bastion for Republicans.

Coffey said he expected Obama to perform well in the northwest part of the state. John Kerry lost that region by a wide margin in 2004, but Obama nearly erased that shortfall in 2008. Coffey also suggested comparing turnout in the largest counties to the collective turnout in smaller rural counties.

“Bush won in 2004 because his campaign had a strong turnout machine in rural areas, and he won by very large margins among these voters,” Coffey wrote in an email. “But, importantly, this helped only because the Bush team matched the Kerry campaign in suburban areas. Ted Strickland lost his reelection bid for governor because of low turnout in urban precincts.”

With that caveat about focusing on individual counties in place, it’s still worth mentioning Wood County. While it is not one of the largest counties in Ohio, Wood has served as a bellwether by picking the winner of every election since 1980.