Velma Hart became an instant celebrity when she told President Obama at a town-hall meeting on CNBC: “Quite frankly, I’m exhausted. I’m exhausted of defending you, defending your administration, defending the mantle of change that I voted for …”

In a follow-up interview with Michelle Singletary of the Washington Post, Hart explained her comments: “I was operating off expectations he set during the campaign trail. I thought there was something special and secret he knew that would make things operate differently … I guess I started to believe on some level that he had a magic wand.”

As the fall campaign enters its final stage, and Obama sweeps around the country, trying to energize voters like Hart who backed him two years ago, he is a victim of his own success. There are no magic wands, no special secrets, and there never were. But for those who believed in magic, their disillusionment is that much deeper, their despair that much more crippling.

Not only did Obama overhype his promises; he underestimated the problems he would face when taking office. As he noted at the town hall, the economy lost 750,000 jobs in January 2009, the month he was inaugurated, and 1.2 million over the next two months. “The challenge,” he said, “is that the hole was so deep a lot of people out there are still hurting.”

Two contradictory vectors fueled this expectations gap: Hopes were soaring just as jobs were disappearing. And now there’s a third factor — pessimism. Many Americans believe those jobs are not coming back, at least not in their towns, and not at the wage levels they once enjoyed. As another questioner told the president: “It feels like the American Dream is not attainable to a lot of us.”

No wonder three out of five Americans say the country is headed in the wrong direction. No wonder Republicans are delighted and Democrats depressed. But the question now is: Can Obama do anything to change the landscape? The economic numbers won’t move over the next five weeks, but what about the public mood? Can he alter enough attitudes, and enough votes, to save the Democratic majorities in Congress?

It doesn’t look good. Obama and his vice president, Joe Biden, are often excoriating Democrats instead of exciting them. At a campaign stop in New Hampshire this week, Biden urged Democrats to “remind our base constituency to stop whining and get out there and look at the alternatives.” The president struck a similar note of self-pity, telling Rolling Stone magazine that “People need to shake off this lethargy. People need to buck up.” Democrats, he added, were acting like spoiled brats who “want to take their ball and go home.”

They’re right, but they come off sounding like Jimmy Carter at his most dyspeptic — not a great political role model. It’s hard to complain about whiners without sounding like a whiner yourself.

Plan B is to convince voters that the economy is “moving in the right direction,” even if folks can’t see or feel the improvement in their own lives. When he makes this case, Obama resembles the law professor he once was, ticking off bills passed and programs enacted to reinforce his message. He even told Rolling Stone that, “I keep in my pocket a checklist of the promises I made during the campaign.”

Well fine, his legislative record is actually good, and he has passed some things that might work in the future. But arguing a case in a courtroom is different than rousing passions in a football stadium. Legal briefs don’t make good campaign slogans. “Accelerate depreciation on business investment!” is not the sort of rallying cry that will get the Velma Harts of the world to the polls in November.

So what’s left? Optimism, that’s what, the most important commodity in American politics. Ronald Reagan understood that, and so did Bill Clinton. During the campaign, Obama did, too. As a slogan, “Yes we can” was a brilliant evocation of the American spirit, but two years in office have sapped the president’s ability to inspire confidence. If Velma Hart seems exhausted, so does Obama.

He needs to follow his own advice. He needs to “shake off this lethargy” and “buck up.” He can’t say happy days are here again. But he can promise that happy days WILL come again. He cannot offer magic wands. But he can offer moving words. Believe in yourself. Believe in us. Believe in America. Believe in the future.

(Steve Roberts’ new book, “From Every End of This Earth” (HarperCollins), was published this fall. Steve and Cokie Roberts can be contacted by e-mail at stevecokie@gmail.com.)