Rep. Paul Ryan (R-Wis.) is among the most disciplined and intellectually rigorous politicians you will find. VP Joe Biden is not. But in a debate, Biden’s all-too-well known weaknesses may become strengths. Biden does not get hung up on details or get into the weeds of legislation. He and his boss have nothing to lose (if you accept that they have lost their lead). So he may let it rip — accusing Ryan of throwing granny over the cliff, the poor to the wolves and the country into serial wars.

Ryan needs to keep several key points in mind.

First, as Mitt Romney showed, it is often preferable to be the counter-puncher and not the aggressor in the debate. He doesn’t need to level Biden or show he is his junkyard dog equal. That isn’t who Ryan is, and coming from someone younger with less experience than Biden a hyper- aggressive approach could well come across as grasping and immature. Better to use humor to slice an opponent than bludgeon him with a rhetorical bat. Better to compliment Biden than to insult him, so long as the target is President Obama.

Second, give details but in limited doses. The entire 2012 budget is not up for debate. Ryan can’t talk about “baselines” and Congressional Budget Office jargon without losing most of the audience. He certainly needs to give examples of what Romney-Ryan would do, but he should not make this into a budget hearing.

Third, he is not running against Biden in any meaningful sense. (Virtually no one is going to cast his vote based on who he’d like to see as VP, and any such voter is likely a solid partisan.) Ryan is there to do two things and two things only: show he could step into the presidency in an emergency, and present Romney’s agenda and case for the presidency.

The former requires projecting steadiness and resolve in substance and in tone. It means keeping his cool when provoked. It means presenting his credentials without seeming like a pushy job applicant. He can calmly remind Biden that they’ve both been around in Congress, achieved more and made a bigger impact on the Hill than Obama did when he waltzed through the Senate on his way to the White House. Given Romney’s superb debate performance, Ryan’s job is not to score a knockout but to go toe-to-toe with the sitting vice president. Calm is better than cutting; solid is infinitely better than sarcastic.

Ryan will certainly be attacked for everything from his abortion record to his budgets. He shouldn’t go into a defensive crouch and can certainly explain his record. But the goal is to present the Romney-Ryan agenda, with the top of the ticket’s policies and priorities front and center. He shouldn’t feel compelled to compare and contrast his record to that of Romney’s; rather he needs to explain why he fully supports Romney’s proposals and why they are better than Obama’s plan.

Ryan can’t sit on the lead or shy away from painting Romney’s agenda in bold colors. If you play not to lose you often do. But the ticket doesn't need Ryan’s debate appearance to change the momentum in the race. His job is to solidify the excellent impression Romney made and to continue to pound home the sharpened message: Unless we get rid of Obama and enact some pro-growth, pro-job initiatives, the country will slide into permanent decay with the middle class slipping further and further behind. In other words, he needs to show the country what the conservatives know he does so effectively, namely present a conservative reform agenda in easily understood terms and project both optimism and common sense. In short, he needs to be the adult in the room, that is, on the stage, Thursday night.