McCain's decision to 'suspend the campaign' is based on well-meaning but outdated thinking.
The rationale goes something like this: convince voters that you are very, very serious-minded about something that is a really overwhelming crisis. This probably will work even better if the crisis is one that the voters themselves are obsessing over, not just the candidates. Would a scheduled debate one week after 9/11 have been postponed (had it been an election year)? Probably so. Or it would have been turned into a bipartisan memorial service. Or something.
In scenarios like that, the campaign has to tread a fine line -- call for a suspension too late, when voters are already accusing you of sticking to politicking when you should be pitching in, and you risk alienation the other way.
This rationale I think appeals strongly to McCain by nature. He believes in the big gesture (e.g., not letting the Vietcong set the admiral's son free ahead of other POW's who'd been there longer). He has an instinct for narrative -- for constructing political narrative out of his life story.
Here's the problem: It's not the 20th century any more. It may well be that the more things change, the more they stay the same, but nowadays it happens so much faster. On Internet-time, the narrative you construct today has to have a compelling Chapter 2 tomorrow, or someone else's narrative will fill the void.
McCain may have imagined that he would get an uptick from his grand gesture -- how selfless, how noble -- but five or six minutes-of-fame later, people are already asking "What have you done for me lately?"
No, Mr. McCain, you don't get the rest of the week to show off your deep concern and unpolitical principles. We've already moved on.