Obama led Republican challenger Mitt Romney by 52 percent to 47 percent, marking the seventh straight time Wisconsin has voted for a Democratic presidential candidate.
In the Senate race, U.S. Rep. Tammy Baldwin claimed victory after posting a 50.7-46.6 percent lead over former Wisconsin Gov. Tommy Thompson with 84 percent of the vote counted.
Baldwin thus became not only the first female U.S. senator from Wisconsin but also the Senate's first openly gay member.
Obama's victory came despite the presence of Wisconsin Congressman Paul Ryan on the Republican ticket as Romney's running mate.
Still, the result was a comedown for Obama from his 14-point victory over Republican Sen. John McCain in 2008.
Ryan, meanwhile, was re-elected to his southern Wisconsin congressional seat, leading Democratic challenger Rob Zerban 58 percent to 40 percent with 65 percent of the vote tallied.