WASHINGTON (Reuters) - Rick Santorum had a one percentage point lead over Mitt Romney in the Republican presidential primary in Ohio on Tuesday, with three quarters of the vote counted.

Santorum, a former U.S. senator from Pennsylvania, was leading with 38 percent to 37 percent for Romney, a former governor from Massachusetts. The two were separated by fewer than 7,000 votes.

(Reporting by Deborah Charles; Editing by Vicki Allen)