Obama is already painted as such by Republicans. He has nothing to lose then, eh? Unless you're saying that he is afraid of the fight (he isn't). Why not look 'Presidential' during an election year? Reason - he intends something highly controversial and not in America's or our allies best interest. He won't get it through the Senate after the election anyway if that's the case. So what's his real problem?
Kennedy got the Limited Test Ban Treaty through in 1963. Clinton continued to negotiate the ABM treaty in 1996. Carter concluded negotiations of SALT II in 1979.
Yes, Obama is as weak as Carter was back in 1979, IMO, but negotiations could still go on and he could still appear quite presidential while pushing back any Senate ratification until after the elections, after all HE is in control of the calendar with any negotiations he chooses to enter into.