The Rasmussen 'Approval Index'

I just sent the following email to the awesome folks at FiveThirtyEight.com who were perhaps the most reliable source of polling analyses during the run up to the November elections. Maybe it's not "folks" - maybe it's all Nate Silver, in which case he's doing yeoman's work in crunching numbers. And if you didn't know, I like numbers. Just put me in a room with a spreadsheet and I'll be a happy camper.

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The right wing Power Line blog has a post called "Regressing Towards the Mean" in which they attribute some significance to the President's "approval index" - i.e. the difference between Strongly Approve and Strongly Disapprove, based on Rasmussen Reports. There are a couple of interesting points to note about the Rasmussen polls:

1) There is a consistent 98-99% response rate for approve/disapprove (A/D). They don't seem to have a Don't Know/No Answer category. A quick survey of most other polls listed at Real Clear Politics puts this at odds with most other polls which have a total A/D response between 80-90%.

2) Rasmussen has also consistently given lower approval ratings and higher disapproval ratings than nearly all other polling agencies. You need only compare past spreads to see that Rasmussen is something of an anomaly when it comes to A/D polling.

So my question is how significant is the Rasmussen approval index and, given the following quote from Power Line, is it really evidence that Republicans should rely on?

The Democrats are trying to follow a "100 days" strategy reminiscent of Roosevelt, in which they will enact a far-reaching transformation of the American economy at the outset of the Obama administration. This approach is based in part on the calculation that Obama's personal popularity and the reluctance of many to attack him (consider the kerfuffle over the New York Post cartoon about the stimulus bill) will help them to ram through Congress a program that contains radical elements that are not supported by the American people. The evidence suggests, however, that Obama does not have such a powerful influence with voters, and that Republicans should not hesitate to do their utmost to block the Democrats' ambitions or to criticize Obama where appropriate.