There’s no doubt President Obama’s liberal supporters are worried by his lackluster performance in the Denver debate. “Everyone is in shock,” one show-business liberal told the Hollywood reporter. “No one can understand what happened.” The Obama faithful are offering the White House advice, talking points, pep talks — anything to improve the president’s performance when he next faces Mitt Romney at Hofstra University on October 16.

But for some liberal writers, the concern goes deeper. Perhaps Obama’s somewhat withdrawn demeanor at the debate was an indication that he doesn’t even want a second term as president.

On the morning after the debate, The Atlantic ran an analysis headlined, “Snippy Obama, Whose Heart’s Not In It.” Writer Garance Franke-Ruta suggested that Obama, as an unusually sensitive man, has been worn down by the presidency’s demands of conducting war in Afghanistan and dealing with crises like the murder of a U.S. ambassador and three other Americans in Libya. “His supporters keep wanting Obama to be who he was in 2008,” Franke-Ruta wrote. “But that’s not who he is anymore.” Obama’s old enthusiasm for the job is simply gone.

Now, in the Daily Beast, liberal writer Michael Tomasky asks, “Does Obama Even Want to Win the Election?” After poor Obama showings at the debate, the Democratic convention, and a high-profile “60 Minutes” interview, Tomasky writes, “Someone needs to ask the cut-to-the-chase question: is he enthusiastic about keeping this job, or he is just maybe tired of being president?”

Perhaps he is. If so, there were certainly signs long before Wednesday night in Denver. A look at the president’s career shows he has never stayed in a job four years without looking to move on to something better.

After a year or two as a community organizer, Obama became deeply frustrated by his inability to enact the kind of big changes in society that he wanted to see. He went to Harvard Law School to plug into the power structure that would help him make those changes in the future. Returning to Chicago three years later, he dabbled in the practice of law before winning a seat in the state Senate in 1996. But he became frustrated with the job almost immediately; according to a Washington Post profile, Obama began “chafing … at the limitations of legislating in Springfield.”

The easily-bored state legislator almost immediately began planning a run for the U.S. House in 2000 — which turned out to be his only losing campaign. Shortly thereafter, he set his sights on the U.S. Senate, winning in 2004.

But within a year after arriving in Washington in early 2005, Obama was restless again. According to the election account Game Change, in 2006 Senate Majority Leader Harry Reid “sensed [Obama's] frustration and impatience, had heard rumblings that Obama was already angling to head back home and take a shot at the Illinois governorship.”

“I know that you don’t like it, doing what you’re doing,” Reid told Obama, according to Game Change. Reid suggested Obama run for president instead. Soon Obama was doing just that.

Now Obama has been president for nearly four years. Aided by a huge Democratic majority from 2009 to 2011, he achieved some big things — massive stimulus, Obamacare, Dodd-Frank. He even won the Nobel Peace Prize, essentially for showing up. But he hasn’t achieved, and won’t achieve in four more years, the “fundamental transformation” of American society that he envisioned. And his entire career suggests that by now he should be angling for a bigger, better job. The problem is, there isn’t such a position — and a second term in the same old job doesn’t count. The chief benefit of winning re-election to a second term might simply be to avoid being labeled a loser, to avoid joining Jimmy Carter and George H.W. Bush as presidents who couldn’t win a second time.

So if his liberal supporters sense signs of boredom and frustration in the president, they might be right. I wrote about this in a January 2010 column that began, “This is about the time Barack Obama becomes bored with his job.” Back then, he had just passed a year in office — about the time, in the past, that his restlessness and ambition began to kick in. Now, years later, the problem is only worse.

UPDATE: More, from the Guardian: “Has a disillusioned Barack Obama lost the will to win?”