Watching the president grimace his way through the restrained back-and-forth reminded me of a conversation I recently had with a friend in Democratic politics, who posited that Mr. Obama simply doesn’t love being president. Not that he doesn’t want the job or believe he should have it, or that its challenges don’t give him plenty of cause for stress or solemnity — just that he doesn’t appear to actually enjoy the daily business of running the country…

The problem for Mr. Obama isn’t that he seemed indifferent or peevish on stage, though he did. The problem is that it underscored what has too often been his countenance in office.

He came to Denver with no larger theme he wanted urgently to get across, no story to tell, no apparent passion for the chance to make himself understood and make his opponent look silly. He was there to defend his policies, but he wasn’t going to get all needy about it, and no one was going to make him have an ounce of fun.

In contrast, Mitt Romney seemed eager to make his case, exhibiting some amount of apparent desperation, like the teenage suitor who has 10 minutes to convince his girlfriend’s father to bless the marriage. That desire to be understood counts for something.