What's sensible? Anything elite centrist opinionmakers think is sensible! So, the political center is an artificial concept created by people who imagine they're centrists because they know they're sensible and they certainly aren't extreme. The fact that such ideas do not have majority support, or don't really fit on the center of some political axis, is irrelevant. It's the sensible center, as they define it.
Whe Kevin Drum writes:
I'd argue, for example, that good analysis supports a fairly extreme view on Social Security (just leave it alone for now)...
He's buying into this "centrism as centrist opinionmakers define it." But how on Earth can wanting to maintain the status quo on a long-existing program which has tremendous majority support be described as an "extreme view"? But all "sensible centrists" know that Social Security is doomed, benefits must be cut, and private accounts are probably a peachy idea, so this becomes a "centrist position."