I'm a little late coming to this, but Jonathan Martin had a good piece Monday thinking through how John McCain's age will play in the general. It's especially timely in light of yesterday's "losing his bearings" back-and-forth.

Jonathan writes:

But some Democrats already have explicitly questioned McCain’s fitness to serve at his age, including Rep. John Murtha, who himself is 75. The Clinton-backing Pennsylvanian has twice tweaked his fellow Vietnam veteran, suggesting first that the presidency was “no old man’s job” and then that McCain’s willingness to keep troops in Iraq for the long term was that of somebody who “doesn't expect to be around” for a second term.

Such shots, delivered by someone from McCain’s own generation with a smile and a chuckle, are the way the issue can be exploited, said Beckel.

“The only people who can attack on this are his age or older,” said Beckel, surmising that a contemporary could not be accused of ageism.

Trotting out a test line to be delivered by Murtha or another elder Democratic statesman, Beckel offered: “’I don’t know about John, but at 73 I can’t put up with that kind of pressure.’”

And, as Scott Reed pointed out, such an issue would have particular resonance among voters in the same age bloc.

“Seniors are the ones who really question [the age factor],” said Reed, Dole’s campaign manager in ’96. “And that’s the voting group that really turns out in national elections.”

That last thought is especially interesting. Obviously the conventional wisdom is that Obama struggles among seniors. Even the Obama campaign concedes the point. Is it possible that his weakness will be neutralized by seniors' skepticism that someone their age would be up to the rigors of the presidency?

P.S. I'll try to track down some polling on the age issue--i.e., how Obama does against McCain among seniors versus, say, how Obama does against Hillary. It won't be definitive by any stretch, but it might give us something to go on.

Update: Gallup's super-helpful data librarian Maura Strausberg sends along some relevant crosstabs:

The May 1-3, 2008 Gallup/USA Today/CNN poll shows McCain beating Obama 55-37 among voters aged 65-and-over.

The same poll had McCain up 51-42 over Hillary among 65-and-overs, and, in the Democratic primary, Hillary over Obama 63-31.

The April 18-20, 2008 Gallup/USA Today poll shows McCain beating Obama 51-40 among 65-and-overs, Hillary beating McCain 48-47, and Hillary over Obama 58-29.

Perhaps more importantly, in each match-up McCain does better among 65-and-overs than he does among voters overall. That doesn't in itself prove McCain won't see some attrition among seniors--marginal differences are what we're after--but I'm skeptical.

--Noam Scheiber