The New York Times‘s Andrew Rosenthal checked in yesterday with a report on the latest Mitt Romney/Chris Christie event in New Hampshire. A line from the end of the report stood out for me.

There was one bad moment — when he quoted a Romney line, that Mr. Obama was “the most pessimistic man I’ve ever seen in the Oval Office.”

The Romney crowd is very proud of that line. I have no idea what it means.

The Romney campaign seems to be preoccupied at times with touting its optimism — not about the Republican nominating race, per se, but just in general about the future. And as part of the same pitch, of course, Romney and his team are also trying to convince us that President Obama isn’t just a pessimist, but he’s actually the “most pessimistic man.”

I know why Romney does this, but it doesn’t make it any less ridiculous.

Whenever this subject comes up, the conventional wisdom generally tells us we’re supposed to think of Ronald Reagan, since “optimism” was a key element of his appeal. It was fundamental, we’re told, to understanding his entire persona — the former president had an infectious optimism.

I tend to think much of this is just hype and p.r., but the myth has endured to the point that it shapes coverage of presidential campaigns. The media scrutinizes contenders based on their capacity to be the “optimistic” candidate.

And campaigns take this seriously, too. In 2004, one of the first big general-election ad buys from the Bush/Cheney camp was for an ad that quoted the then-president saying, “I’m optimistic about America because I believe in the people of America.” A voice over said John Kerry was “talking about the Great Depression. One thing’s sure — pessimism never created a job.”

And here we are again, with the GOP frontrunner complaining about the president being “pessimistic.”

There are two broad problems with the Romney campaign’s pitch.

The first is that there is a pessimistic vision on the table, but it’s not from Democrats. In his debt-reduction speech in April, Obama took on Paul Ryan’s House Republican budget plan from a variety of directions, but he specifically noted, “I believe [the GOP plan] paints a vision of our future that is deeply pessimistic.”

It’s a compelling charge. Not only are Republicans miserable about the present, they’re also presenting a dour vision of the future, with the elderly, low-income families, students, small businesses, and struggling communities all left to fend for themselves. How does Mitt Romney’s vision differ from congressional Republicans’ vision? It doesn’t.

The other problem here is that Barack Obama has an unyielding optimism that’s hard to miss. The president delivered a speech to supporters in D.C. last night and the remarks are worth reading — the crux of the speech was about how optimistic he is.

Romney’s clearly invested in this, but it’s a mistake. Voters are supposed to believe Mr. Hope and Yes We Can is “the most pessimistic” president in modern times? Even Obama’s harshest critics are going to have a tough time buying it.

Steve Benen

Follow Steve on Twitter @stevebenen. Steve Benen is a producer at MSNBC's The Rachel Maddow Show. He was the principal contributor to the Washington Monthly's Political Animal blog from August 2008 until January 2012.