Ed Kilgore has an excellent post on the oddly backward nature of John McCain's current "biography tour" and the general weirdness of the campaign emphasizing the idea that their candidate is genetically programmed to monger war through his jingoistic heritage (or something). Ed notes the analogy to Bob Dole's 1996 campaign, the last time the GOP thought having an old man talk fondly about long-past suffering was a good way to win elections. Relatedly, I think it was Matt Stoller who pointed out recently that the candidate with the more impressive military record lost in 1992 and 1996 and 2000 and 2004 so there's reason to doubt that McCain's genuinely impressive military record will serve as an ace in the hole for his campaign.
What I'll say on behalf of this strategy is that it's the best way I can think of to try to take advantage of older people's potential discomfort with the idea of a woman or a black man in the White House that doesn't involve exploiting racism or sexism in a discreditable way. McCain's putting together an identity politics counter-narrative steeped in nostalgia; it didn't work against a white southerner running on a very cautious agenda, but 2008 is going to see the Democrats nominating an unorthodox candidate running on a more liberal agenda.
To me, though, one primary issue in a McCain-Obama race is going to be how successful McCain can be at obscuring his enormous hostility to America's public sector retirement infrastructure. McCain's record, and that of his key economic advisors, is pretty clear -- these are people who want to gut Social Security and Medicare in order to clear budgetary space for an agenda of low taxes and many wars. The resulting situation will be fine for those senior citizens who, like McCain, had the foresight to divorce their first wife in order to marry an heiress and then secure a congressional pension, but others may not achieve such happy results. That could all be very damaging to McCain's old people strategy, but to be damaging Democrats will need to move on to the general election first.