In 2010, the Ohio election law was amended to require all qualified parties to certify the names of their presidential and vice-presidential nominees by 90 days before the general election. In 2012, that would be August 8. However, neither the Democratic Party, nor the Republican Party, will have held their national conventions that early.
The Ohio law is section 3505.10(B). It says the November ballot, in presidential years, will include “the names of the candidates for president and vice-president certified to the secretary of state or nominated in one of the following manners: (1) Nominated by the national convention of a political party to which delegates and alternates were elected in this state at the next preceding primary election. A political party certifying candidates so nominated shall certify the names of those candidates to the secretary of state on or before the 90th day before the day of the general election.”
Texas had a similar problem in 2008. The law required the names to be certified by a date that was earlier than the date of the Republican and Democratic national conventions. The Secretary of State did not enforce the deadline in 2008, and in 2009 the Texas legislature repealed the deadline. The Ohio legislature is still in session so it could fix the problem if it wished.