THE SECOND presidential debate was snappier than the first and useful in illuminating contrasts in personality and political philosophy between President Obama and former Massachusetts governor 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 assume that the principal conundrums of the next term will be how to lower taxes on the middle class 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. Among the cuts are reductions to defense spending that Defense Secretary Leon Panetta has warned would be catastrophic to national security. If any of this is to be avoided, a reelected Mr. Obama or a President-elect Romney will have to work with the lame-duck Congress to fashion some way out.

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. The country has to find a way not to undermine recovery in the short term while getting debt under control in the longer term. The alternative — the track we are on — will see health-care spending and interest payments crowd out just about every other government function.

Both candidates know that, to avoid that grim scenario as the population ages, Americans will have to make some sacrifices. Taxes are going to go up, and not just on the rich. The retirement age will have to be pushed back.

Yet regarding the fiscal cliff, neither candidate had one word to offer. And on the longer-term challenge, here’s what Mr. Romney had to say: “I want to get middle-income taxpayers to have lower taxes.” And Mr. Obama: “I want to give middle-class families and folks who are striving to get into the middle class some relief.” Mr. Obama attacked his opponent for refusing to raise taxes on the rich. Mr. Romney glancingly attacked the president for having failed to reform Medicare. And that was it.

The discussion on energy presented a similarly dismal picture. “Few challenges facing America — and the world — are more urgent than combating climate change,” Mr. Obama said. “Now is the time to confront this challenge once and for all. Delay is no longer an option. Denial is no longer an acceptable response.”

Don’t remember those words? That’s because Mr. Obama spoke them in 2008, just after his election. At Tuesday’s debate, there was no mention of climate change. Instead, Mr. Obama boasted of “increases in coal production” during his first term. Mr. Romney assailed him because he “has not been Mr. Oil, or Mr. Gas, or Mr. Coal” — these being the fuels that are warming the climate, coal above all.

Many voters do not want to hear about sacrifice — about carbon taxes or benefit cuts. But true leaders occasionally look beyond their focus-group results.