The same environment would also influence a a McCain presidency, but the conservative social forces and program of the Republican party are additional fetters on change. The liberal base and program of the Democrats have the contrary potential to move an Obama or Clinton administration further in the direction of reform, in much the same way preceding generations of Democrats and the social movements they belonged to did so in the case of FDR and JFK. This is the fundamental difference between the parties; the differences are less apparent at the level of the candidates.
The excitement around Obama is reminiscent of Trudeaumania in Canada as well as the rise of JFK, which the Obama campaign has fashioned itself after. It's easy to be repelled by the excitement around a slick young bourgeois politician which quickly becomes its own justification in a celebrity-worshipping media-driven culture, but these electoral upsurges at the same time also represent a pent-up longing for change which energizes a new generation and brings it into the political sphere. It's the latter dimesion of Obamamania which atracts leftists like Julio who have no illusions about the candidates responsible for this political motion.
Whether these movements actually move to a higher level depends on whether the economic and/or foreign policy crises which spawn them either deepen or become more manageable. Historically, of course, the crises have been mostly contained, and the hopes for deeper change awakened in the electorate have been mostly disappointed.