We all know that President Obama needs a better night than he had in the first debate. But the entire Democratic political apparatus and Obama’s own supporters also need a better night than they had last time. Who prevails this evening depends not only on how each candidate does but also on how their supporters react.

Mitt Romney cannot play it as if he has the election in hand. He doesn’t. He still needs to overcome that indelible moment when he consigned 47 percent of Americans to the hopelessly dependent category. And he can’t say anything goofy or unfeeling, his habit at so many points in the campaign — but something he avoided in Debate One. My hunch is that Romney will try to surprise Obama again, as he did in their first debate by throwing off his right-wing, GOP-primary self and playing at being more moderate. Obama needs to be ready for a second Romney surprise.

A lot has been written about how Obama needs to go on the attack, but attack isn’t quite what he needs. First and foremost, he needs to show that he really wants to keep his job, and that he’s happy to fight for it. The most disconcerting aspect of the first debate wasn’t that Obama failed to go after Romney’s shape-shifting and untruths, though that was a problem. It’s that Obama was utterly disengaged and seemed to have no desire to battle for a second term. A number of Obama supporters I spoke with after Debate One said they felt that were fighting harder for Obama’s reelection than he was. This time, he needs to convey spirit, energy and a little joy.

Yes, he has to call out Romney, but he can do so with humor and good cheer. Obama has to point out as he goes along how Romney’s numbers don’t add up, but he needs to use narratives and compelling examples, not indecipherable math. He also needs to show that the impact of Romney’s policies will be to lift up the already privileged, and that trickle-down doesn’t work. Vice President Biden prepared the ground for this argument. Obama does not need to be as forceful as Biden was precisely because Biden did his job effectively. This debate should be seen as the second step in a two-step recovery process begun by Biden in his debate with Paul Ryan.

And, yes, as my colleagues Harold Meyerson and Gene Robinson both pointed out in their columns today, Obama needs to tell the country where he wants to lead it.

 But there is another aspect of tonight, and that’s the part played by the staffs of the two candidates and their supporters. What people say during the debate — Twitter has really changed things — matters a lot. So does what happens after it’s over and how it’s interpreted and spun. These things can matter almost as much as the debate itself.

The Obama campaign simply could not offset the highly negative assessments of the president’s performance in the first debate that extended far beyond the world of Fox News. Team Obama could not manage to break through with any negative talking points about how Romney performed: the fact that Romney seemed overly caffeinated, hyped-up in attack mode, and that he said some things that were flatly untrue.

 Notice, as others have pointed out in the past few days, that Republican spin-meisters did not worry in the least that they might have contradicted themselves by saying that Romney’s aggressiveness against Obama was a sign of leadership while Biden’s aggressiveness against Ryan was a sign of disrespect. Oh, yes, they would offer talking points about how the two performances were actually different, but they are not really worried about the contradictions because they know that this process of ours doesn’t reward intellectual consistency. No matter what Obama does tonight, be ready for an argument from Team Romney that Obama “overcompensated” in Debate Two by being too aggressive, while Romney looked “presidential.” I can guarantee it, even though I won’t bet you $10,000.

 Finally, watch what Obama’s supporters make of the debate. Keep an eye on the Twitter feeds and on what the more liberal commentators say in their post-debate commentaries. As the first presidential debate went on, the feeds of progressives went almost silent. After the debate, Obama-leaning commentators might have been even more critical of his performance than neutral analysts were. The negativity built and metastasized to the point where Obama’s “defeat” looked far worse 24 and 48 hours later than it did at the time. To invoke a football metaphor, it would be as if post-game commentary had the power to spin a 24-to-14 defeat into a 38-to-3 catastrophe. That can’t happen in sports, but it can happen in political debates.

 My hunch is that this won’t be repeated this time — partly because Obama’s supporters have been put in a fighting mood by the possibility of a Romney victory, and partly because Obama rarely makes the same mistake twice.

But it does come back to Obama and Romney. Romney’s is a fairly simple recipe: Look empathetic and don’t say anything dumb. Obama has to turn in a performance that gives his spinners and supporters positive things to say. He can start by looking happy, determined and engaged. His slogan is “Forward.” His main substantive task is to explain what this means.