How long will Election Day last in Ohio?

— -- COLUMBUS, Ohio—Tightly knotted Ohio has become this year's making-of-the-president state, pivotal to the White House strategies of Barack Obama and especially Mitt Romney. Amid all the victory hype by both sides, Republican and Democratic insiders surprisingly agree about the idiosyncratic rhythms and odd contours of election night in the Buckeye state.

Based on bipartisan interviews conducted with the promise of no-quotes-please anonymity, I have put together this likely scenario for election night return-watching in Ohio:

Around 8:30 p.m. (the Ohio polls close at 7:30 p.m.), the first big wave of returns will sweep onto the tote boards. These are the absentee ballots and early votes (maybe 35 percent of the statewide total of about 5.8 million) that the Democrats have been particularly aggressive in harvesting. At this moment, Obama will almost certainly hold his biggest Ohio lead of the evening in percentage terms.

That Obama margin will dwindle throughout the evening as the returns from Ohioans who waited until Election Day to vote are added to the total. By 3 a.m. Wednesday, when virtually all the statewide votes have been tallied, Romney may have moved into the lead. Does that mean that the Republicans can claim Ohio's 18 electoral votes?

Tune in to ABCNews.com on Tuesday, Nov. 6 for livestreaming coverage of Election 2012. Our Election Day show kicks off at noon, and the Election Night event begins at 7 p.m.

Not so fast. For in the wee hours Wednesday morning, the counties will begin their count of the provisional ballots. These are votes that have been challenged for a wide variety of legitimate reasons. They include: Ohioans who are not registered; registered voters who moved but failed to update their addresses; people who showed up at the right polling place but were directed to the wrong precinct; voters who did not bring proper identification to the polls; and those who requested an absentee ballot but decided to vote in person.

Before anyone shouts, "Voter suppression," please understand that the bulk of these provisional ballots eventually will be counted. In 2008, around 80 percent of the provisional ballots were ultimately accepted and that figure rose to about 90 percent in the 2010 gubernatorial race. Recent Ohio history has shown that the provisional ballots tilt strongly Democratic when they are finally tallied. And that is what could make Republicans very nervous as Tuesday night flows into Wednesday morning.

The rough Republican rule of thumb is that Romney requires a statewide lead of, at least, 50,000 votes to survive the provisional ballot phase of the Ohio long count. The requisite election night margin for Romney may, in fact, need to be higher. It all depends on the number of provisional ballots plus valid absentee ballots (postmarked Monday or earlier), which are still in the mail. And despite the best efforts of the secretary of state's office to release an accurate count of disputed and missing ballots Wednesday morning, the final numbers will probably trickle in from Ohio's 88 counties over the following few days.

At this point, under some plausible scenarios, neither Obama nor Romney may be able to claim the White House without Ohio's 18 electoral votes. Despite the whole-world-is-watching drama, events onstage in Ohio will begin to unfold at the pace of Freudian analysis.