I'd think that not even an Obama could continuously be elected because the presidency is the living embodiment of the State. It is the very face of the rotting shell of bourgeois sham democracy. When the constant internal contradictions inherent to it's very existence inevitably arise and through the decay, pillaging and outright destruction of their lives rouse the masses into gaining political consciousness, their collective ire focuses upon the arbitrator of the struggle between the working class and the capitalist class. But because the Capitalist class is entrenched itself within the State and in turn puppeteers it, the capitalists in their pursuit for monopoly on the wealth of the world turn upon itself and fractures itself into factions who's only common interest in keeping the working class out of power and themselves in. Thus these factions, with the rules they've drawn up for themselves to make their theatrical game fair for themselves and unfair to us, perform to the irate masses to rally support to their faction with the promise of salving the contradictions that've roused them in anger in exchange for their support in ousting their opposition that sits in the majority.

An obama type may last longer, but they would not be immune to the backlash that occurs under their rule when crisis' occur. I don't even think a true social democrat on the level of FDR at his peak of power could make no term limits work even if his political base was secure and filled with succdems, socialists, and communists and he ensured that he had a pool of good successor candidates to ensure the transfer of power between living people goes smoothly through the years. The prime contradiction of the irreconcilable antagonism between the classes and the role of the bourgeois state in arbitrating it will inevitably see the roll back of concessions gained and further exploitation of the working class.