Liar.
It's public info. She donate to Gore's '88 campaign for President, and Lloyd Bentsen before that.
That doesn't mean she's a democrat today, but seeing that we don't know anything about her - and probably won't during the confirmation hearings, since she'll certainly employ the Ginsburg Method - all we can say is, she's probably a centrist at this point with the possibility of being a stealth conservative.
There are a plethora of known quantitites - conservative originalists - who would make it through confirmation, albeit with some scars at the end. But if you want to satisfy the base, you don't throw out Harriet Miers. You throw out a known quantity that says "I've listened to your vote".