ROVE

Posted at 2:36 p.m. ET

Karl Rove, based on his own excellent instincts, and after speaking with scholars on the subject, has this take on the impact of Sarah Palin over the next two months:

Taking on Alaska's good-old-boy politics and beating the incumbent Republican governor might be seen as evidence of the political courage and independence voters are looking for this year. And with women more undecided than men, Mrs. Palin could add more than a point to Mr. McCain's total -- maybe two or three -- which could make the difference in a close contest.

Note the numbers.  Historically, even outstanding vice-presidential choices have had only limited impact.  Could this year, though, be different?

The threat Mrs. Palin poses is why Mr. Obama's campaign has moved rapidly to disparage her record, and why left-wing bloggers have engaged in nonstop character smears against her and her family. Some in the press have aided and abetted this because they feel left out of the preannouncement vetting process. The danger for Democrats is twofold: in highlighting Mrs. Palin's inexperience, they may focus attention on Mr. Obama's; and the harsh attacks levied against Mrs. Palin could completely undermine the Obama promise of a "new politics." In the vice-presidential debate, Democrats must be concerned about Mr. Biden appearing bombastic and condescending -- which is almost a permanent state of mind for the Delaware senator -- while Mrs. Palin comes across as fresh, straight talking, nonpolitical and therefore appealing.

I say, let Biden be Biden!  It could help us.

This will be history's shortest general-election campaign. The race is tight, so every new variable carries substantial risk and opportunity. So while the GOP vice-presidential pick is by far the more creative and bold, it is also the more dangerous.

But even if Mrs. Palin does well, as I believe she will, it is still Mr. McCain's performance in the next 61 days that will matter most. Sarah Palin can help advance the McCain reform narrative, but the hard work still rests squarely on the shoulders of John McCain. And that's exactly where the maverick and war hero wants it.

Which is why tonight's speech is so critical.  John McCain doesn't generally do well in set speeches, but his campaign staff knows it.  I have to believe they've prepared him well. 

Look for the following things:  Tracking polls in the next five days, and the size and intensity of crowds as McCain and Palin go out on the campaign trail.  Will Palin now become the phenomenon the GOP hopes, or will her appeal be limited to those already converted?

We're going to get some important answers in the next week.

September 4, 2008.