First, he has to show up. Then, in his second debate with Mitt Romney, President Obama needs to offer not just history lessons and dire warnings, but also a hopeful vision for the next four years.

It would be hard for Obama to turn in a worse performance Tuesday night at Hofstra University than he did at the first debate in Denver. All he has to do is show a little energy and enthusiasm, and the next morning’s headlines will surely be full of “comeback” metaphors. But that’s not enough.

Obama’s passivity in the first debate was so striking, and so surprising, that it overshadowed all the other ways in which the president failed. Romney came with a story to tell — a fraudulent story, to be sure, since it so contradicted the tale he told during the Republican primaries, but a well-crafted story nonetheless. Obama came, apparently, with a handsome necktie.

Romney now seeks to portray himself as an unthreateningly moderate technocrat, as opposed to the “severely conservative” ideologue we met earlier this year. One of Obama’s more easily achievable goals Tuesday night should be to remind voters — and perhaps Romney himself, who seems to forget — of previous Romney positions such as “self-deportation” for undocumented immigrants.

In the first debate, Romney’s worst moment was when he tried, and failed, to explain how he would cut income tax rates by 20 percent without adding a penny to the deficit. Obama tried to note the inconsistency, but Romney bulled his way through by simply insisting that up was, in fact, down. “Strong and wrong” shouldn’t trump “weak and right,” but in a debate it often does. I’d suggest the president think about perhaps raising his voice every once in a while, especially when Romney says things that cannot possibly be true.

I’d also suggest that the president prepare — and practice, in front of an audience or at least a mirror — his closing statement. Wrong approach: “I said that I’m not a perfect man and I wouldn’t be a perfect president.” Right approach: anything else.

And please, no looking down at the podium, even to take notes. If necessary, aides should confiscate any writing implements before the president takes the stage. He can look at Romney, at the moderator, at the audience, at the camera — anywhere but down.

Body language is important. Millions of Americans are proud of the accomplishments of the Obama administration. The president should look as if he is, too.

These are relatively easy fixes. The bigger and more important task is demonstrating to Americans they will have a brighter future with Obama in the White House for four more years.

This was Obama’s biggest failure of the first debate — or rather, Romney’s biggest success. Romney promised to lead the nation to a Valhalla of jobs and prosperity. It was a cynical, empty promise because he offers nothing more than a repackaging of the trickle-down policies that have brought us to this parlous state. But Romney was forceful, hopeful and optimistic, and my reading of the post-debate polls is that substantial numbers of undecided voters were impressed.

It’s necessary — but not enough — for Obama to call him on this deceit. Obama also needs to make his own promises to the American people. And unlike Romney’s, they can even be genuine.

In Denver, Obama pledged to fight for the middle class. That’s an admirable sentiment, but it doesn’t go nearly far enough. Obama needs to explain how the policies he has implemented, and those he plans to pursue, will make our lives better.

Under his administration, the economy has created more than four million private-sector jobs. The nation has taken a huge step toward universal health insurance, and soon will come a day when Americans don’t face bankruptcy just because they become ill. We are more sensibly exploiting our reserves of oil and natural gas while actively seeking to develop the energy sources of the future. We’re engaged in an ambitious program of nation-building here at home — in education and infrastructure, especially — to ensure that we enjoy another American Century.

Romney’s real success in the first debate was to look past the challenges the nation faces, and focus on the opportunities he sees ahead. Obama has to do more than explain why Romney’s vision is a mirage. The president has to tell us what he sees on the horizon, and why that’s the direction we must go.