In February 2010, I sat down to talk health-care policy with Rep. Paul Ryan. Ryan wasn't yet the lion of the right that he is today, but he had a reputation as an unusually wonkish legislator, and he didn't disappoint. In the interview, he was clearly well-versed on the issues, fluent in both his ideas and the main critiques. He was also refreshingly willing to step off-message, as when he admitted that we're always, constantly rationing health care -- the question is simply how we ration health care.

In March, I interviewed Ryan again, this time about his criticisms of the Affordable Care Act. In July, we talked about his ideas for the economy.

J.D. Pooley/AP

Ryan was, for awhile, my favorite interview, as he was willing to do something most politicians weren't: Have a free-ranging, substantive, on-the-record conversation with someone who doesn't agree with him. As he rose through the ranks of the Republican Party, his press strategy changed, and he ended those interviews. Our most recent back-and-forth, which was over his Medicare plan, was conducted, at the insistence of his office, over the relative safety of e-mail.

The upshot is that, over the past few years, I've spent a good number of hours arguing policy with Ryan, and an even larger number of hours trying to understand his policies. So what have I learned?

First, he's smart. This shouldn't need to be said, but some liberals seem to think Ryan's intelligence is some kind of facade. In this view, he's really a robotic Randian who does little more than spout talking points. His reputation for intelligence is simply the soft bigotry of Washington's low expectations for politicians.

Vice President Biden's team would be unwise to buy into this comforting line of thought. Ryan's smart, and he's quick, and he's heard most of what you have to say before. The main mistake politicians make is that they don't listen to criticism of their ideas -- or, even worse, they never put themselves in a position to receive that criticism in the first place. Ryan's different. He's sufficiently engaged in the policy conversation that he knows both the arguments for and the arguments against his positions.

That's not to say he always has good answers for them. I remember walking away from our first debate somewhat confused. The deeper we drilled into the regulations in Ryan's plan, the more they sounded like the very plans he was arguing against.

For instance, he didn't like that in Obamacare, "You’re having a person design how insurance can be sold." Then how does his plan make sure people aren't sold defective products? "In the Patient’s Choice Act, we do an actuarially equivalent minimum in each exchange that’s equal to the Blue Cross/Blue Shield Standard Option." Well, isn't that pretty much what Obamacare does?

What followed was health-care word salad. "The Senate bill goes a lot further than that. You need to define what insurance is. I agree with that. But what we’re trying to achieve here is a system in which the patient is the driver of it, not government bureaucrats." Then how come you've got government bureaucrats deciding what insurance is?

In effect, Ryan's plan and Obama's plan would regulate insurance products sold through the exchanges in pretty much the same way. But Ryan didn't want to say that. So he basically offered a lot of convincing sounding words on the topic. If you parse his response, it's not terribly convincing. But you really need to know the issues to parse his response. The fact that you've caught Ryan in a bit of a contradiction doesn't mean he's going to admit it.

That said, Ryan is very good at admitting when you've got a point. He doesn't do this when you've got a point that undermines his point, but he does it, and generously, when you've got a point that he can agree to. He's also very good at admitting when Republicans have strayed from conservative ideals in the past. You can see that in our discussion of the economy, where he suggests he's eager to fight Republicans over paying for their budget promises, even though he himself was one of those Republicans voting not to pay for anything in the Bush years.

The result is that, while he's a highly ideological thinker, he doesn't come off as particularly ideological. He comes off as an affable, decent, conservative guy who holds strong views, but recognizes that he doesn't have all the answers and that his party hasn't always lived up to its promises.

The other thing you'll see in my discussions with Ryan is that he's happy to get deep, deep into the weeds. As I understand it, this is something he's explicitly trying to work on in advance of his debate with Biden. As a Ryan adviser told National Review's Robert Costa, “he doesn’t want to be the guy talking about CBO baselines."

In my view, that's probably a mistake. One danger for Ryan in this debate is that he spends so much time trying to be someone other than himself that he ends up tamping down on the qualities that made him such an effective messenger in the first place. You saw this happen, to some degree, at the Republican Convention, where Ryan delivered an almost policy-free speech that included so many misleading lines and flat falsehoods that it  led to a quick backlash. He would have been better off delivering a dense, detailed indictment of the president's record. Whatever you think of his arguments, he's good enough at that sort of thing that it launched him from unknown budget guy to VP candidate in about two years.

But his bigger problem is that he's not defending his own policies anymore. Back in the day, Ryan's budgets reflected Ryan's ideas, and when he wanted to say something impolitic -- like that his budget meant rationing health care -- he just said it. Today, he's had to produce a series of budgets that the entirety of the GOP could get behind, which meant tossing some past policies (like Social Security privatization and his health-care plan) overboard and trying to make up savings by tightening his Medicare voucher and making bizarre claims about future spending on non-entitlements.

In this, he's caught between a rock and a hard place. He can't defend these policies anymore, because they're not part of the Romney-Ryan platform, But it looks evasive to pretend to disown them. Saying Romney is the top of the ticket doesn't mean much when you're the guy who will replace him if anything goes wrong. So Ryan will have to answer for two occasionally contradictory sets of policy ideas that often conflict with Romney's agenda. That's going to be difficult.

Ryan also needs to defend Romney's budget promises, which are, if anything, more extreme than his: Where Ryan looks for $5.3 trillion in savings over the next decade, Romney is looking for $7 trillion. Romney also erases Ryan's Medicare savings and increases defense spending, which means he needs even deeper cuts to domestic programs to make the numbers work. That leads to some very difficult-to-defend priorities, like deeply cutting health care for the poor in order to resist raising taxes on the rich. And while Biden isn't very good at arguing numbers, he's very, very good at arguing values.

In a way, the Ryan-Biden match-up is like one of those classic video game match-ups where you pit the burly wrestler against the lithe ninja. The two debaters have completely different strengths. Ryan is a wonk who tends to make abstract budget promises that lead to questions he can't quite answer about the human consequences. Biden is a non-wonk who sees human consequences more clearly than he sees budgets, and when he gets tripped up, it's usually because he got too loose and said something that was meant to be folksy but that came out as offensive. In a way, their strengths are perfectly matched to exploit the other's weaknesses.

It's going to be a fun debate.