The prize could be thousands of traditionally elusive voters in hard-fought Ohio who would have the chance to register and vote on the same day.
The one-stop voting Tuesday through Oct. 6 would be especially convenient for those Democratic-leaning voters who have traditionally had more trouble getting to the polls.
It's a reality not lost on two parties locked in a tight race four years after President Bush's 118,000 vote victory in Ohio gave him a second term.
Ohio is one of more than 30 states that allow registered voters to cast an early ballot. Eight states allow voters to register and vote on Election Day, while North Carolina allows the practice during early voting.
In the six states that had same-day registration and voting before 2006, as well as in North Dakota (which doesn't have voter registration), turnout has been 10 percent to 17 percent higher than the national average, according to the National Conference of State Legislatures.
The battle rests on a reading of the law by the state's Democratic Secretary of State, which has been rejected by some of the state's Republican election officials.
On Thursday two Ohio Supreme Court justices removed themselves from cases involving challenges to early voting procedures, clearing the way for a Democrat to join the all-Republican court making decisions in this hotly-contested swing state.
Justices Evelyn Lundberg Stratton and Maureen O'Connor stepped down from deciding a challenge to a weeklong period beginning Sept. 30 during which new voters can register to vote and cast an absentee ballot on the same day.
The justices also recused themselves from two separate cases in which voters are challenging Secretary of State Jennifer Brunner's decision to reject absentee ballot applications administered by the campaign of Republican presidential candidate John McCain because they weren't filled out properly.
The McCain campaign is reported to have mailed out over a million absentee ballot applications in several states which contained errors. Application forms sent to Ohio voters contained an extra (unnecessary) box which, if not checked, indicates the voter is not eligible to vote.
Hundreds of applications were ruled ineligible in Hamilton County alone.
Republicans have said it's a blatant attempt by Brunner to disenfranchise Republican voters, while Brunner has said the law is clear that boxes on such forms must be checked.
Per normal protocol, the two justices did not provide a reason for stepping aside. But both Republicans are running for re-election on this year's ballot.
Stratton will be replaced by William Wolff Jr., a Democrat on the Second District Court of Appeals. O'Connor will be replaced by Republican Lynn Slaby of the Ninth District Court of Appeals. Both are retiring after completing their current terms.
Chief Justice Thomas Moyer wanted to ensure that there's confidence that the decisions are made by an independent and impartial panel, said Ohio Supreme Court spokesman Chris Davey.
"Chief Justice Moyer wanted to find replacement judges for this case who will be retiring at the end of this term and would represent, to the extent possible, diversity of party affiliation," Davey said.
Ohio Republicans have accused Brunner of bold partisanship for instructing county boards of elections to have procedures in place to allow voters to register and vote on the same day from Sept. 30 through Oct. 6. They have said Ohio law requires voters to have been registered for at least 30 days before they can cast a ballot.
Brunner says the law recognizes a person to have voted when that ballot is counted on Nov. 4, not when it is cast.
The overlap between the beginning of absentee voting and the end of registration has been in law since 1981. Brunner has pointed out that it never got any attention until the Republican-controlled Legislature passed a bill in 2005 that enabled all Ohioans to vote absentee without having to provide a reason, such as being out of state. The Nov. 4 election marks the first time the law has applied during a presidential election year.
Democrat Barack Obama's campaign has said it will take advantage of the overlap period, and groups such as the Northeast Ohio Coalition for the Homeless have said they will drive homeless and low-income voters to the polls during the time.
On Wednesday, the American Civil Liberties Union of Ohio filed a lawsuit asking a federal court in Cleveland to declare that newly-registered Ohio voters must be allowed to vote absentee. The ACLU is concerned about the lawsuit before the Ohio Supreme Court, and filed the federal suit as a backstop measure in case the court rules against Brunner.
The organization said federal law is clear that voters cannot be required to register more than 30 days before an election.
The interpretation of state law advanced by Republicans would preclude some absentee voting even outside the weeklong window, said ACLU of Ohio staff attorney Carrie Davis.
The ACLU sued Madison County, where the county prosecutor advised the elections board not to allow voters to register and vote on the same day next week. Prosecutors in Holmes and Miami counties gave their boards the same advice.
Madison County, just southwest of Columbus, will follow the prosecutor's advice instead of Brunner's unless the Ohio Supreme Court rules in her favor, said Board of Elections Director Tim Ward.
If no court decision comes down before Tuesday, the county will not permit same-day registration and voting, Ward said.
Meanwhile, on Friday the Ohio GOP filed a federal lawsuit to challenge the early voting period. Republicans say state law does not allow same-day registration and voting.
Brunner spokesman Jeff Ortega said, "It appears that some partisans continue to inject chaos and confusion into our election system just five days before early voting starts."
Amid the legal wrangling, preparations for the window are progressing.
Registering The Disenfranchised
Obama's campaign will send staffers to the Ohio State University, the nation's largest campus with about 53,000 students, to encourage early voting among the sometimes hard-to-engage young. Polls show the Democrat is easily carrying the demographic against Republican John McCain.
The campaign plans to arrange concerts from John Legend, who will hold early voting rallies on Monday in Columbus, Springfield, Dayton and Cincinnati. For campuses far from election boards, Obama aides are organizing car pools to make sure students get to the polls.
On Saturday, the campaign targeted the 100,000-strong college football crowd at Ohio Stadium with a flyover advertising early voting and visits from staffers to surrounding bars.
Beyond colleges, the campaign knows it has to do well in Cuyahoga County, the state's largest and the center of Democratic power in Ohio.
The Northeast Ohio Coalition for the Homeless believes it can round up 2,000 people from homeless shelters in the Cleveland area and get them to polling places. A donated van will shuttle voters from two shelters, including the city's largest downtown. Seventeen other shelters are providing their own transportation.
"It'll be fantastic," said Brian Davis, the coalition's executive director.
Project Vote, which pushes for greater voting participation, will go door to door in minority neighborhoods and use vans to transport people to election sites in Cleveland, Cincinnati, Columbus, Dayton and Toledo.
"The populations that we focus on, the lower income and minority populations, move more often," said Teresa James, an attorney working in northeast Ohio for Project Vote. "They're also more likely to have jobs that aren't flexible in terms of voting."
The progressive Rock the Vote will have a bus tour through Columbus, Dayton, Wilberforce, Athens, Cleveland and Bowling Green - all metro areas or college towns - to emphasize the convenience of the calendar overlap.
Cleveland City Councilwoman Stephanie Howse said activists and Obama volunteers are spreading the word in her ward.
"It's just one piece of our much larger approach to early voting to turn out as many people as possible to get those votes in the bank," Obama spokesman Isaac Baker said.
The McCain campaign didn't directly address whether it had plans to take advantage of the window.
"We have a comprehensive grassroots program designed to turn out McCain-Palin supporters once early voting begins," said spokesman Paul Lindsay.