Several networks projected Obama edged Romney in the key swing state. With 74 percent of precincts counted, CNN said the president had 2,162,012 votes to 2,131,776 for the former Massachusetts governor, a 50 percent to 49 percent margin.
The margin was much smaller than four years ago, when Obama won by 4.6 percentage points. George W. Bush won the state in 2004. No Republican candidate in decades has won the presidency without winning Ohio.
Democratic U.S. Sen. Sherrod Brown defeated Republican challenger Josh Mandel. The state treasurer and Iraq war veteran had been tagged with Ohio Politifact's "Pants on Fire" rating for his campaign rhetoric, including unsubstantiated claims that votes cast by Brown were responsible for Ohio jobs being moved to China.
Ohio's 16th Congressional District was considered a tossup where freshman Republican Rep. Jim Renacci squared off against Democratic Rep. Betty Sutton, who got thrown into the 16th District through redistricting after representing the 13th District for three terms. Renacci canceled his TV ads in the campaign's final days to focus on direct advertising.
Republicans gained control of the state Legislature in 2010 and after redistricting, the Pew Center on the States' Stateline news website said that was unlikely to change this year.