In an interview from a few months ago, Palin discusses the Supreme Court’s decision to limit the damages payed by Exxon for the Exxon Valdez oil spill. While she’s not saying anything that requires an advanced degree, she’s articulate, poised and confident.

But in the CBS News footage last night, she’s incapable of naming a Supreme Court decision, other than Roe v. Wade, that she disagrees with.

The contrast is simply remarkable. Is the McCain campaign playing some high-level head fake to make what will likely be a decent performance by Palin in the debate seem like the work of a superhero? This I doubt. But the contrast does lends credence to other possible explanations for why Palin’s performance has gotten worse over time.

In particular: that she’s being overly coached by the McCain team and that she’s “lost her voice” by being put in the position of making and defending claims she knows aren’t entirely true, such as those involving her role in the “Bridge to Nowhere” fiasco.

I also suspect that she’s still trying to master the plethora of McCain’s platform; she is, after all, expected to agree with and defend a range of policies that she had little knowledge about only a matter of weeks ago. She’s got to be under enormous pressure not to say anything (else) that contradicts McCain’s positions, his lines of attack on Obama, or that might offend Republican interest groups. Indeed, she probably knows full well that bashing the Supreme Court for limiting punitive damages isn’t something that will play well with many Republican voters in the “lower forty eight.” No wonder she played dumb on the Supreme Court question.