President Barack Obama and GOP nominee Mitt Romney are squaring off at 9 p.m. ET Wednesday at Colorado's University of Denver. For a primer on what's in store, check out our viewer's guide, or take a walk down memory lane to see how both Romney and Obama have fared in past debates. Leading up to tonight's debate, both sides have been trying to lower voters' expectations, and many pundits say that no matter how many zingers are thrown out, the debates won't actually decide the election. Still, the debate has high stakes, so be sure to tune in.