The pundits are up in arms. How could Congressman Bob Inglis, with a lifetime ACU score of 93+, possibly lose his primary? (And by 42 points no less!) How could Senator Bennett, with a life ACU of 83+, have been sunk at the Utah GOP convention? What are these crazy tea-baggers thinking?
The ACU score is sometimes a useful yard stick. I've used it myself to guesstimate which Congressional districts might be up for grabs, and to see how far a Republican can go in the moderate-to-liberal direction before he or she makes serious waves among the Republican base. (Broadly speaking, 60's is squishy but generally tolerable, 50-ish is the danger zone, and anything below 50 means serious heartburn of the Specter and Chafee variety.)
But fundamentally, the ACU score is based on a flawed model, and we should be careful not to misapply ACU scores. Politics is not uni-dimensional. It's not bi-dimensional. It is not even entirely rational from a technical perspective, so any model relying on simple distributions is going to fail from time to time.
This is one of those times.
Let's look at Inglis. Since losing, Inglis has thrown a temper tantrum against tea partiers, accusing them of racism and demagoguery, and going on Chris Matthews' show as a stooge so Matthews could beat up on conservatives. If this is any indication of how he behaved before the election, then his constituents were right to give him the boot. Inglis voted to ban standard incandescent light bulbs -- hardly a conservative sentiment, and an issue that literally reaches into every home in America and tells people how to live. He voted for TARP, and against a troop surge in Iraq. (Both of those latter issues are debatable on the merits, but one can see where Inglis has transgressed the party line.) And he ran a decidedly negative campaign, which certainly didn't improve his image. In short, Inglis went DC-native, so to speak.
Now, by National Journal's reckoning, Inglis is a 76% Republican, which is still pretty Republican by most standards. But it isn't 93.
And really, that's not even the point. The point is that the ideological distribution curve has broken down in a serious way. Voters, base voters and swing voters, are heavily discounting ideological considerations in favor of candidates who say appealing things about how to address the nation's problems. What people normally think of as "conservative" and "liberal" carries much less weight than it has in previous years.
When politicians lose touch with what the electorate wants, they get axed. That has almost nothing to do with ideology.
So when I see proclamations of everlasting doom because the Republicans nominated some "tea party candidates" here and there, I've got to take that with a grain of salt. Strike that -- a huge, industrial sized salt-lick.