Consider for a moment what the big game is here. This is a battle between two candidates to demonstrate toughness on national security. Toughness is a unitary quality, really -- a personal, characterological quality rather than one rooted in policy or divisible in any real way. So both sides are trying to prove to undecided voters either that they're tougher than the other guy or at least tough enough for the job.
In a post-9/11 environment, obviously, this question of strength, toughness or resolve is particularly salient. That, of course, is why so much of this debate is about war and military service in the first place.
One way -- perhaps the best way -- to demonstrate someone's lack of toughness or strength is to attack them and show they are either unwilling or unable to defend themselves -- thus the rough slang I used above. And that I think is a big part of what is happening here. Someone who can't or won't defend themselves certainly isn't someone you can depend upon to defend you.
Demonstrating Kerry's unwillingness to defend himself (if Bush can do that) is a far more tangible sign of what he's made of than wartime experiences of thirty years ago.
Hitting someone and not having them hit back hurts the morale of that person's supporters, buoys the confidence of your own backers (particularly if many tend toward an authoritarian mindset) and tends to make the person who's receiving the hits into an object of contempt (even if also possibly also one of sympathy) in the eyes of the uncommitted.
This is certainly what Bush's father did to Michael Dukakis and, sadly, it is what Bush himself did, to a great degree, to Al Gore.
In other ways, Bush's bully-boy campaign tactics play to his strengths, albeit unstated and unlovely ones. Many of the polls of the president have shown that while people don't necessarily agree with the specific policies he's pursued abroad many also intuitively believe that there's no one who will hit back harder. There's some of that 'he may be a son-of-a-bitch but he's our son-of-a-bitch' quality to the president's support on national security issues.
This meta-message behind the president's attacks on Kerry's war record is more consequential than many believe. So hitting back hard was critical on many levels.
