If a president is elected on his first term, he will only make so much change. So he makes sure he is reelected. On his 2nd term he wont get reelected anymore so he makes a vast number of changes then. Watch history and the effective changes made by 2nd term presidents.
Also, Obama has kinda become an idol to the public. He hasent done anything outstanding beside catching osama. So he's very likely to be voted in again since he hasent fucked anything up yet and has osama under his belt.