Good straight analysis by Mike Allen at Politico about tonight's debate between Biden and Ryan:

Conversations with advisers to the V.P. candidates suggest that both will be very aggressive tonight. One of Vice President Biden's missions is to calm down President Obama's supporters -- particularly the progressives who, in the view of the White House, have overreacted to the disappointing first debate. Biden plans to do that by making Ryan answer for his own proposals, as well as Romney's. The V.P. wants to stay more on offense than on defense, and expose and explain contrasts. His style is to demonstrate a mastery of specifics, then step back in "Regular Joe" style to relate to viewers. His prep team in Wilmington, Del., included Ron Klain and Bruce Reed. His mock debates were formal, but aides dressed casually.

PAUL RYAN has been watching game film of Biden, including the '08 debate with Sarah Palin and the V.P.'s "Meet the Press" appearance in May, to try to get in his head. Since the Republican convention, Ryan has been buried in a pair of debate-prep binders - one for foreign issues, one for domestic. As Ryan rewrote and edited his responses, the drafts were sent to Boston for fact-checking, then added to the binders. Ryan plans to call out the President and Vice President for what he considers mischaracterizations of GOP positions, and will argue that he has worked hard on these measures, and knows they are being mis-described.

Ryan aides argue that Biden should be a great debater, both because of his 36 years in the Senate and decades on the national stage. They point out that in 1988, when Biden was seeking the Democratic presidential nomination, Ryan was in high school.

Don't expect fireworks. The stakes are too high to take a chance on generating controversy. Both men will tread carefully when on the attack, trying hard not to make it sound personal. Biden may have more experience, but Ryan has spent much of the last year defending his proposals and knows what works with audiences. Having to defend Romney, however, may cause Ryan some problems for the simple reason that the guy at the top of the ticket hasn't been very consistent in his views.

The question I have is has Biden been overprepped? He has spent the last 6 days off the campaign trail prepping for the debate. Not to be too unkind, but Biden will be 70 next month and the mind just isn't as supple and flexible at that age as it was perhaps even 4 years ago. Biden is going up against a man considered brilliant by many. That doesn't necessarily mean that Ryan has a leg up on the vice president, but it does mean he will have his hands full with his younger opponent.

Will Biden blow it? Matt Latimer:

On Thursday night, it will be Joe Biden and Paul Ryan's turn to shift the winds again with gusts of hot air.  At his best, Mr. Ryan is a young(ish) idea guy who is a rarity in politics: someone who actually believes what he says. At his worst, Ryan can come across as a heartless number cruncher-or the most physically fit accountant in Janesville, Wisconsin.

Unless Mr. Ryan lights the podium on fire or walks on stage in a tank top, however, most eyes will be trained firmly on our current vice president. And Mr. Biden has the trickier task-to reinvigorate the Obama campaign's momentum while making the case against Mitt Romney that his boss seemed to think was beneath him. Can Joe Biden pull off such a task? Well, that all depends on which Joe Biden decides to show up.

Latimer wonders if "Dan Quayle the Second" and his gaffetastic personae will show up, or "Bazooka Joe" who can lay out the zingers with the best of them will be on stage. We're likely to see both, as we are likely to see Ryan become too pedantic at times, get too far into the weeds of policy for a general debate audience.

We'll see just how much people care about the performance of the #2 guy on the ticket.