ABC News' Michael Falcone reports: 
 
 UPDATED: COLUMBUS, Ohio - Even if Rick Santorum wins Ohio on Super Tuesday, he won't be able to claim all of its delegates. In fact, he is at risk of forfeiting more than one-quarter of them. 
 
 In three of the state's 16 congressional districts, including two that are near Ohio's border with Pennsylvania, Santorum will lose any delegates he might have won because his campaign failed to meet the state's eligibility requirements months ago. 
 
 Those three districts alone take 9 delegates out of a total of 66 off the table for Santorum. 
 
 But it gets worse: Nine more Ohio delegates may also be in jeopardy. 
 
 Sources say that in six other congressional districts - the third, fourth, eighth, tenth, twelfth and sixteenth - Santorum submitted fewer names than required to be eligible for all three delegates up-for-grabs in each district. 
 
 That means even if he wins in those places, he might not be able to receive the full contingent of delegates. 
 
 In the three districts where Santorum did not submit a delegate slate at all, he will not be able to receive any delegates. In the six where he submitted only a partial slate, he is eligible to be awarded only the number of delegates he submitted, assuming he wins a particular district. 
 
 Chris Maloney, a spokesman for the Ohio Republican Party, said the leftover delegates will be considered "unbound" and the campaigns will be able to file a petition with the state party to claim them. Once such a petition is filed, Ohio GOP Chairman Kevin DeWine is required to impanel a "committee on contests" composed of three members of the Ohio GOP's central committee to sort out the delegate awards. 
 
 What's clear is that Santorum will be competing in Ohio on Tuesday handicapped by the fact that he is ineligible to receive nine delegates and perhaps as many as nine more, or more than one-quarter of the state's delegates. 
 
 Worse yet, some of these problem districts are in areas of the state where Santorum is expected to do well. The sixth congressional district, for example, hugs Ohio's eastern border with West Virginia and Pennsylvania - the state Santorum represented in Congress. The thirteenth district, which includes Akron, is nearby. 
 
 Notably, Santorum plans to spend election night in old steel town of Steubenville, Ohio, located in the sixth district, even though he has no chance of collecting any of the district's three delegates. 
 
 The bar to file what's known in election parlance as a "full slate of delegates" in each district was not particularly high. Candidates were required to submit the names of three delegates and three alternates per district. 
 
 According to the Ohio GOP, the Santorum campaign is missing the names of one delegate in the state's third district, two in the fourth, one delegate in the eighth, two delegates in the tenth, one delegate in the twelfth and two delegates in the sixteenth. Santorum's opponents - Mitt Romney, Ron Paul and Newt Gingrich - each filed full slates in all of Ohio's districts as did two candidates who are no longer in the race, Rick Perry and Jon Huntsman. 
 
 In other words, Santorum needed to submit 48 names in order to be eligible to compete for all of state's district delegates outright. 
 
 Santorum is facing a high-stakes contest with Romney in Ohio. A Quinnipiac University poll released on Friday showed the former Pennsylvania senator with a slim four percentage point lead over Romney in the state, 35 percent to 31 percent. Roughly one-third of likely Republican primary voters said they could still change their mind before Tuesday. 
 
 And as the Republican nominating contest becomes as much a battle for delegates as it is for momentum, Santorum's difficulties in Ohio offer another window into the organizational challenges his campaign has faced throughout the primary season. Santorum is not on the ballot in Virginia, which also holds a primary on Super Tuesday and where each candidate was required to submit 10,000 signatures, including 400 from each of the state's 11 congressional districts. 
 
 The eligibility requirements in Ohio were comparatively easier, but at the time Santorum's rivals were putting together their delegate slates in December, Santorum was crisscrossing Iowa in a pickup truck ahead of the caucuses, which he ended up winning by a hair. The deadline for submitting the slates in Ohio was the last week of December. 
 
 There are a total of 63 delegates up for grabs in Ohio on Tuesday, 48 of them are awarded proportionally based on who wins the popular vote in each Congressional district - three per district - and 15 will be awarded to the candidate who wins a majority of votes in the state. However, if no candidate surpasses 50 percent of the vote, the "at-large" delegates are awarded proportionally to each candidate who received more than 20 percent of the statewide vote. Three additional party leaders will act as unbound delegates at the Republican National Convention, but they will not be awarded on Tuesday. 
 
 The Romney and Santorum campaigns offered vastly different takes on the delegate situation in Ohio. 
 
 "The attempt by the establishment to to deceive the voters of Ohio and further their hand-picked candidate will be met with resistance on Tuesday. I want to be clear, Rick Santorum's name will appear on every ballot in the state of Ohio and every vote cast will go towards his At-Large Delegate Allocation," Santorum campaign communications director Hogan Gidley told ABC News. "As it relates to individual Congressional Districts, it's clear we aren't the establishment hand-picked candidate and back in December we were a small effort focused on Iowa. Now that we've won several states Obviously much has changed and we feel confident that we will do well in both the delegate and popular vote count on Tuesday." 
 
 Romney campaign spokesman Ryan Williams said that the Santorum campaign's shortcomings in the state was a sign of weakness. 
 
 "Rick Santorum has failed to get on the ballot in Virginia, has failed to file full delegate slates in Tennessee, New Hampshire and Illinois, and has failed to submit enough delegates in several Ohio congressional districts," Williams said in a statement. "The fact that he cannot execute the simple tasks that are required to win the Republican nomination proves that Rick Santorum is incapable of taking on President Obama's formidable political machine." ||||| UPDATED with new information 
 
 WASHINGTON -- Rick Santorum was already known as starting from a deficit, delegate-wise, in Ohio. He failed to qualify for any district delegates in three Ohio congressional districts because he didn't turn in delegate names there. 
 
 But his delegate troubles go deeper. According to the Ohio Republican Party tonight, the former Pennsylvania U.S. senator filed incomplete delegate slates in six additional Ohio districts. 
 
 Altogether, this means Santorum, who until this week had a fair lead in polls in the Republican nominating race, could be ineligible for 18 Ohio district delegates. 
 
 Ohio has 66 delegates total, 63 at stake next Tuesday. The candidate with the most delegates wins. Santorum therefore goes into the Ohio primary election with a 29 percent deficit. 
 
 What will happen if he wins in a district where he failed to allocate a full slate of three delegates? 
 
 In the short term, he will be eligible to take only the delegates he has already allocated in that district, the party says. Yet he will have won that district -- so the unallocated delegates will not be awarded to anyone else, either. 
 
 After all, they did not win them. 
 
 "On Super Tuesday, if Sen. Santorum were to carry a district where he has not seated a full delegate slate, he will be awarded delegates where he has submitted delegate names," said Ohio Republican Party spokesman Chris Maloney. "And the additional delegates in that district will be unallocated." 
 
 This almost certainly sets up challenges, if not from Santorum then from political rivals such as Mitt Romney or Newt Gingrich. 
 
 The state party says it has not faced this situation before, but it has been reviewing its bylaws and is prepared, if there is a challenge, to convene what it calls a "committee on contests." 
 
 State Republican Chairman Kevin DeWine would appoint three party members to the committee, and they would make a recommendation to the state party's central committee, which would rule. 
 
 If Santorum or another candidate did not like the ruling, he could appeal to the Republican National Committee. 
 
 ABC News' The Note broke the story this evening. 
 
 The Ohio Republican Party says it discovered Santorum's problem this week. While candidates were supposed to file their delegate slates with the Ohio secretary of state as well as the state party, Santorum only filed his with the secretary of state. The secretary of state, however, has no authority over delegate counts. That office merely needs to make sure that a candidate has qualified with a bare minimum of delegates to get on the ballot. 
 
 Secretary of State Jon Husted's office did that, according to the state Republican Party. In the three congressional districts where Santorum filed no slates of delegates whatsoever, Husted's office ruled that Santorum would be ineligible to be on the ballot for district-delegate purposes. This has been known and reported for some time. 
 
 Santorum's name will be on ballots in those districts for purposes of another kind of delegate, however, based on the statewide popular vote. In other words, all other candidates will have their names on the ballot twice -- once for district delegates, once for the state delegates. But there are far fewer state delegates to be won than there are district delegates. 
 
 The Ohio Republican Party, saying it never got a slate of delegates from the Santorum campaign, got a copy from Husted's office, according to one official. The party needed to review delegate slates in preparation for next week's election. It was only then that it realized there was a problem and began informing all the candidates this week. 
 
 Ohio has 16 congressional districts, or will for purposes of this election. (It now has 18 but will lose two at the end of 2012.) Romney, Gingrich and Ron Paul have slates of three delegates in each. But here is how Santorum's slates shake out: 
 
 District 1: 3 delegates 
 
 District 2: 3 delegates 
 
 District 3: 2 delegates 
 
 District 4: 1 delegate 
 
 District 5: 3 delegates 
 
 District 6: 0 delegates 
 
 District 7: 3 delegates 
 
 District 8: 2 delegates 
 
 District 9: 0 delegates 
 
 District 10: 1 delegate 
 
 District 11: 3 delegates 
 
 District 12: 2 delegates 
 
 District 13: 0 delegates 
 
 District 14: 3 delegates 
 
 District 15: 3 delegates 
 
 District 16: 1 delegate 
 
 This could get interesting, and difficult, for Santorum because his failure includes districts where he might otherwise run well. 
 
 He was already at a 3-delegate deficit, for example, in the Steubenville area (District 13) and another 3-delegate deficit further south on Ohio's eastern border (District 6), areas where steel workers and others might remember him from his days serving Pennsylvania. He has campaigned in that region anyway; Santorum's grandfather was a coal miner, as are some of the area's residents. 
 
 And he has his other 3-delegate deficit on the West Side of Cleveland and some of its suburbs (District 9). While Romney has been expected to perform better in Northeast Ohio in general, Santorum's social conservative message could appeal to Catholic voters in the western neighborhoods and suburbs. 
 
 But Santorum also has diminished his chances in socially conservative counties like Allen, Shelby and Auglaze (District 4) and -- this is noteworthy -- Montgomery, Greene and Fayette counties (District 10). The latter two can be considered Mike DeWine country. DeWine got his political start in Greene and still has his home there. As state attorney general, DeWine is Santorum's highest-profile supporter in Ohio. Akron, too (District 16), is now problematic for Santorum. 
 
 A Santorum spokesman has not returned a message seeking comment. But Santorum is in Lake County tonight, where reporters are certain to ask about this. The campaign of his chief competitor, Mitt Romney, has already pounced on Santorum's apparent error.
– Rick Santorum may be at the top of the polls in Ohio, but even if he wins there, he may not win. Because his campaign missed several eligibility deadlines, he could lose up to 18 of the state's 63 available delegates, report the Cleveland Plain Dealer and ABC News. In nine districts, Santorum's campaign filed either incomplete delegate slates or none at all. Even worse, several of those problematic districts are areas where Santorum was expected to perform well. Santorum is not even on the ballot in Virginia, and failed to file full slates in Tennessee, New Hampshire, and Illinois, but the eligibility requirements in Ohio were considered easier. Santorum's campaign said that because he is one of the leading candidates in the GOP primaries, he should—and will—receive the full delegate count he wins on Tuesday, but the Romney campaign disagreed. “The fact that he cannot execute the simple tasks that are required to win the Republican nomination proves that Rick Santorum is incapable of taking on President Obama’s formidable political machine," said the campaign. The state party would have the final say.