The candidates had taken turns showing meager leads late into the night, and both spoke to their supporters without declaring victory.
Both candidates had crisscrossed the Buckeye State in recent days, making their pitches to voters.
Despite the uncertainty, Santorum took to the Steubenville High School stage Tuesday evening to declare his campaign was not going away anytime soon.
Mr. Santorum added Tennessee, North Dakota and Oklahoma to his tally of victories Tuesday night and credited his scrappy campaign’s message for the series of victories across the country over the past two months.
Mr. Romney also carried Alaska, Idaho, Vermont, Virginia and Massachusetts.
Ohio, one of ten states that voted on Tuesday, has sixty-six delegates up for grabs.
Mr. Santorum will be ineligible for some of those delegates because he failed to qualify for the ballot in some Ohio congressional districts, including the one where his victory party was held Tuesday night.