CBS News chief Washington correspondent Bob Schieffer: "This is the most anticipated, and will be the most closely watched vice presidential candidate speech I can recall. Usually it's all about what the candidate says in his speech. But there's far more interest in what she's going to say.
"It's because no one knows who she is. She simply has to, number 1, not make some sort of blunder, which I don't think she will… but what she has got to do is introduce herself to the American people. Every poll shows the vast majority of the American people have no idea who she is. First impressions are always the most important.
"I think this is something that is either going to be seen as one of the most astute and smartest nominations in the history of politics, or it's going to be a flop. I don't think there is going to be any in between."
CBS News political analyst Joe Trippi: "I think she's got to use this moment not to so much explain any of the controversies around her, but explain who she is and to take her strengths -- her strength of reform, taking on corruption -- and project that as to how that affects the McCain-Obama fight.
"The more she is defensive, the more she's unsure, the worse it is… There are going to be plenty of times immediately after all this where the press is going to get to ask her all those questions… Explaining it tonight is not going to do her or McCain any good.
"If she talks about her family, it should be making the case for who she is, why she brings a different view to the campaign. She's a woman -- she's got a different perspective. And she's a governor, which is also a different perspective. And she's taken on corruption, even within her own party.
As for her overall goal tonight: "It's to present those positives and not to dwell on a whole lot of the questions. I think it's going be pretty heavy handed on the reform stuff."
CBS News political analyst Dan Bartlett: "She has to define herself for the American people in a way that is not only compelling, but convincing that she is worthy of the number 2 spot on the ticket for the Republicans. It's a rare political opportunity for a candidate to unfiltered tell their own story. So this is a big moment, the stakes are high – the question is whether she can step up to the plate and knock it out."
Bartlett agrees that she shouldn't talk about the controversies surrounding her this week.
"Maybe a veiled humorous reference swipe at her critics would be far more effective than trying to do any sort of laundry list approach to the allegations."
As for expectations: "The irony is that they are almost as high as Barack Obama's speech at Invesco field. She has rocked the political world and she has been the entire political story since her announcement. And I think it has got the entire collective interest of the American people, so this is a big moment."