It's a big mistake to discount Palin tonight. Yeah, she's appeared as an ill-prepared, out of her league wannabe in the Couric interview, but the format of tonight's debate definitely favors her strong points--90 second responses, sitting down, etc. and the McCain campaign has been in overdrive to manage expectations no matter her performance

The word from the DNC is that they have prepped her to go nasty. That's a warning for Biden, who--if he falls in the trap--could damage himself by appearing to be patronizing or too aggressive towards her.

But this could be a make or break moment for the slowly slipping McCain campaign. As Howard Fineman says on today's Hardball, Palin's performance tonight will reflect McCain's judgment: