Specifically,

McCain advisers said they were only somewhat concerned about Ms. Palin’s debating skills compared with those of Mr. Biden, who has served six terms in the Senate, or about Mr. Biden’s chances of tripping up Ms. Palin. Instead, they say, they wanted Ms. Palin to have opportunities to present Mr. McCain’s positions, rather than spending time talking about her own experience or playing defense.

So the McCain campaign doesn't want voters to judge Gov. Palin for herself, even though she'd be one step from the Presidency if McCain is elected. They don't want her to talk about her experience only McCain's positions.

I've said before I think Palin canceled so many campaign appearances this week to be able to spend more time at debate camp. It now looks like on debate night, all we'll learn is how quick a study she is, not what she believes or whether she's qualified or prepared to lead the nation either as Vice President, or if events so dictate, as President.