Death Spiral

Agreed:

Most fundamentally of all, the McCain campaign radically overestimated the importance of appealing to the base. House Republicans may be replicating their mistake. Self-described conservative Republicans represent only about 20 percent of the population. This base is not necessarily becoming smaller; it's still alive and kicking. What is true, however, is that the (1) base has never been sufficient to form a winning electoral coalition, and (2) that there are fewer and fewer non-base (e.g. moderates, libertarian Republicans, Republican leaning-independents). As these moderates have fled the GOP, the party's electoral fortunes have tanked. But simultaneously, they have had less and less influence on the Republican message.

Thus the Republicans, arguably, are in something of a death spiral. The more conservative, partisan, and strident their message becomes, the more they alienate non-base Republicans. But the more they alienate non-base Republicans, the fewer of them are left to worry about appeasing. Thus, their message becomes continually more appealing to the base -- but more conservative, partisan, and strident to the rest of us. And the process loops back upon itself.