The most important tool the California press had to use against Simon was that he was an extreme conservative, an outsider, an unknown lacking experience, who did not have Bush's confidence or the support of the California Republican leadership. They are still saying that the dark-horse Simon only beat Riordan because Gray Davis ran an ad campaign against Riordan--which is clearly not true and probably won't get them much mileage.
No, the important thing is that President Bush supports Simon and is happy to campaign for him. Sending Laura Bush is essentially the same thing. It's a very positive signal, and there's no way the press can distort that simple fact--that George Bush supports Bill Simon.
You are completely right. And, in some ways, sending Laura Bush to California shows more support than coming himself. Laura is his wife and partner in every sense of the words, and they obviously care about each other. I don't think he would ask her to do something she either didn't want to do or didn't feel comfortable with, or if he was only playing games out here in California. He wouldn't use his wife to play games.
At least, that's my impression.