The second presidential debate was snappier than the first and useful in illuminating contrasts in personality and political philosophy between President Obama and Mitt Romney. But as a guide to actions either man might take in response to the biggest challenges he will face, the debate -- like most of this campaign -- was close to useless.

Someone tuning in for the first time Tuesday night might have assumed that the principal conundrums of the next term will be how to lower taxes and how to mine more coal.

The reality is starkly different. On Jan. 1, even before the next president is inaugurated, a series of tax hikes and spending cuts is due to take effect, and the Congressional Budget Office has flatly warned it would send the nation back into recession.

This so-called fiscal cliff is only the most immediate test in the longer-term challenge that will surely consume much of the president's term: how to get the nation's fiscal house in order.