President George W. Bush won Ohio and several other close contests in 2004 on the strength of his campaign’s organization, turning an election he easily could’ve lost into a victory by a surprising three million popular votes.

Barack Obama is hoping to stage a comeback victory in tomorrow’s Ohio primary based on a similar movement of political “ground troops.”

This strategy has worked for the Illinois senator so far nationally, catapulting him into the lead, albeit slightly, in a Democratic race where he had little name recognition and establishment support as recently as December.

It certainly helps when you give incredible speeches and can outspend your rival to build your coalition, but it’s grass roots support that has enabled Obama to stage a number of primary and caucus wins, coast to coast - many of them routs.

Can he do it in Ohio - where Hillary Clinton was an overwhelming favorite among the blue-collar workers who form much of the Democrats’ base?

By now, Barack Obama has done all he can personally. It will be up to his legions of followers on the ground to deliver a victory in tomorrow’s Ohio primary.

As Tuesday’s primary approaches, the battleground shifts from TV ads and massive rallies to the simple, all-important task of turning out the vote.

The deciding factor in winning that task could be as simple as the number - and the passion - of the two candidates’ ground forces.

Web-recruited staffers and canvassers were armed with call lists and sheets of Barack Obama’s policy positions, taking to the streets and phone lines.

It’s how Obama has competed with Clinton from Iowa on.

Carefully plotted maps are being distributed to groups headed out to visit Buckeye State voters door-to-door, and forms bearing fresh updates on all occupants of each home visited were collected from returning Obama volunteers.

It’s been a year in the making for the Barack Obama camp, as volunteers have been staffing major Democratic events across the state, gathering and sorting voter contact information, recruiting volunteers and directing donors.

Will it be enough? The proportional delegate allocation tomorrow means a big swing for either contender is unlikely, but the popular vote will tell us a lot.

The Ohio primary is the toughest test yet for Obama, and a chance for him to test his mettle in a swing state where he began as a huge underdog.