Why agent-based modeling is important

Here's a good example of the sort of thing that agent-based modeling can do that other approaches can't. This blog post from Capital Gains and Games talks about why

Mitch McConnell (R-KY) … announced—proudly—that he would not allow an increase in the debt ceiling without significant cuts in Medicare?

At first blush this may not seem like that big of a deal given the continuing demands from the GOP leadership in the House for substantial spending cuts before it will allow a debt ceiling increase. But it is. This is not a call for reductions in general; it's insisting on cuts in an exceedingly popular specific program. And it's not just any specific program: It's Medicare, the currently most politically sensitive program of all and the one that, because of the Republican plan to make substantial reductions, cost the GOP a House seat in upstate New York just barely a week ago.…

So why did he do it? According to the Stan Collender, the post author and a perceptive political observer,

1. McConnell likely can't stay as minority leader without unequivocal support from the GOP's tea party-like base and, in the wake of the widespread criticism of Newt Gingrich for abandoning the House GOP Medicare reduction plan (Newt was against it before he was for it), he used this statement and extreme position to shore up his own bona fides with that wing of the party.
2. McConnell wants to be majority leader if the GOP takes over the Senate and needs the base to do that.
3. McConnell is from the state that also elected Rand Paul to the Senate and he runs the chance of looking like a liberal Democrat in comparison to his junior senator if he doesn't make statements like this.

[Perhaps] McConnell has decided that the GOP winning the White House in 2012 isn't as important to him as the GOP getting the majority in the Senate and that requires continually energizing the base rather than trying to win over independents and Democrats.

If Obama wins and the GOP takes over the Senate, McConnell will be the most important and powerful Republican in the United States…Roger Ailes aside. That won't be true if there's a Republican president, of course. But if all of the best known GOP candidates lose the Republican nomination in 2012 and the 2012 nominee then loses in the general election, the next tranche of potential Republican presidential candidates will be at least two years away.

Only an agent-based model in which McConnell is modeled individually could account for that sort of action. No general model of relative political power could do anything like it.