A quote that Jackson supposedly said (debated historically) would be accurate in this situation.
First, he would need to be compelled by Congress and possibly the SC. Do you really think that is going to happen? After that, it would fall on the Executive Branch to enforce it.” __________________________________________
I think you are probably right on the possible institutional hurdles, but “illigitimate” and “unConstitutional” are still powerful words. Obama bears the burden of proof to answer a ligitimate and constitutional question. In the absence of proof, he will eventually be compelled to withdraw his candidacy for 2012, or, in the absence of institutional and enforcement action, he will be declared ineligible by enough states to cause his withdrawal. Also, the prospect of America being ruled by a “foreign agent” of sorts, in defiance of the Constitution, may be found to be a bridge too far for the Independents, who will decide the election.
Individual states control who gets on their ballots, so states can make this into an issue. I would expect a court challenge if they do, though.