I've been fascinated with the implications of John McCain's age on the presidential campaign for a while now. For all the talk about Americans' comfort levels when it comes to an African-American president or woman president, there's ample evidence that voters are even more concerned with a septuagenarian president.

Howard Dean recently noted that the DNC doesn't plan to touch this during the general election, saying, "There is somewhat of a higher ethical bar on what we do."

Yesterday, however, John Murtha went there.

Rep. Jack Murtha, who has endorsed Hillary Clinton's presidential bid, introduced the New York senator at a Washington appearance Wednesday with the observation that Sen. John McCain is too old to be president. "It's no old man's job," said Murtha.

McCain is 72, three years younger than Murtha, a powerful Democratic congressman from Pennsylvania. Murtha said the demands of the office were too much for men of their age. If he were elected, McCain would be the oldest first-term U.S. president in history.

"...[T]his one guy running is about as old as me," said Murtha. "And let me tell you something, it's not [an] old man's job. I mean the campaign, the stress, so forth."

An unhappy McCain campaign spokesperson responded, "I think people will evaluate John McCain through the type of campaign he is running, whether it is through appearances on shows like Letterman and Leno, whether it's through the fifteen hour days on the campaign trail."

McCain's age isn't cause for concern because he can appear on Letterman? That's the response? McCain must be in good shape for a 71-year-old man because he can stay up until 11:30? (What if the phone rings at 3 a.m.?)

As for Murtha, it's smart for him to make the charge that McCain's too old to be president because he's older than McCain. If Obama or Clinton repeated his remarks, it'd come across as offensive and insulting. But if a fellow septuagenarian says the same thing, it's harder to accuse him of ageism. Murtha is effectively saying, "I'm too old to be president, and so is he."