Why have gas prices skyrocketed over the past few months?

Over the last 10 years, gas prices increased an average of 22%. Since April 2007, it has increased 25% and is up 31% in the last few months. I have heard different arguments about keeping up with inflation, fuel efficient vehicles, refining techniques, etc; but I think $4 per gallon gas is absurd. And why aren't the presidential candidates doing something to at least slow it down?