My guess is the fight would go down something like this:
Obama starts chanting, demonically "Hope, change, hope, change, hope change...." as he slowly approaches McCain pounding his fist into his palm.
McCain, losing his temper after just a few seconds of the monotone chant, begins to snarl. "What an annoying battlecry", he thinks to himself. Just then, his wife blurts out from the spectators "Don't worry honey, it's all smoke and mirrors, there is no substance in that attack".
Obama, realizing McCain's old lady just ruined plan A, quickly thrusts his palms forward, Ryu style. But instead of shouting "Hadukin!" he shouts "Yes we can"!
McCain, being great with age, and not spry enough, is unable to dodge the incoming blue fireball. The fireball, amazingly, hits him with all the force of a of a puff of smoke. He exchanges the snarl for a few moments for a look of confusion. Again, his wife shouts from the sidelines. "Don't worry honey, he puts on a fantastic show, but there is nothing underneath the hood!"
Obama, furious that his plan has been spoiled, and determined more than ever to win, does the unthinkable. Muttering a spell, he summons a demon pet; the demon known as "wright", the only real force with a strong position Obama has ever encountered. The demon "wright" begins to charge at McCain, but then stops dead in his tracks, spins around looking Obama in the eye and says "Screw you man, you betrayed me". The demon "wright" then disappears.
McCain, now way too angry to think clearly or come up with a strategy, stops within feet of Obama and shouts "I know your weakness, B.O!! You will sell out our economy to environmental alarmism, do nothing to stop dependence on foreign oil, and leave the cobwebs on our immigration enforcement!"
Obama, without missing a beat, replies "So will you, old man".
McCain, now more furious than ever, screams "You bastard! If you are elected you will at best maintain our taxes, at worst increase them while trying to nationalize all you can. Plus, you really have no firm stance or plan for anything and only wait for polls to determine your positions. And lastly, you are a not-so-closet Marxist!"
Obama, appearing bored now, again replies "Are you insane? You describe yourself as well!"
McCain, tired from being so angry now, is finally able to think clearly. He realizes Obama is right and says "Well why are we fighting then?"
Obama answers "Because the American people expect it and need it."
McCain smiles "Oh. Right. Well then, come let me buy you a prune juice, and hope nobody saw this silly encounter." As they walk off, McCain asks "Why would anyone vote for either of us anyway?". Obama replies "What choice do they have?". McCain chuckles "Good point".