Who against the America President Obama?

Answer 1

If you are asking who ran against him in the 2012 presidential campaign, the main candidate to oppose the president was the Republican, Mitt Romney. But there were other candidates from smaller and lesser-known parties, including Gary Johnson, the Libertarian Party candidate, and Jill Stein who ran for the Green Party. But if you are asking who is against him-- as in, who disagrees with him-- since he received 51% of the vote, we may assume that everyone else, while perhaps not 100% "against" him, did not want him to be re-elected.