This much is clear: President Obama could have learned a thing or two by watching his understudy last night. Vice President Joe Biden was aggressive, pro-active, and on the attack from the get go. He looked into the camera, addressed viewers personally, and used plain, simple language as he drove his points home. But his derisive interruptions of his opponent — the finger-wagging and teeth-baring grin — seemed a bit over the top, and detracted from his overall performance.

What about Paul Ryan? The Republican challenger, who was just 3 years old when Biden first arrived on Capitol Hill, was cool, calm, and methodical. He looked good, and often sounded wiser than his 42 years. The future seems bright for the man from Janesville. But he was wrong — if not outright misleading — on several occasions, and, when caught admitting he privately asked for stimulus funds while publicly criticizing the program, looked downright hypocritical. 

As usual, both sides see things quite differently. "Rudeness is the weak man's imitation of strength," Republicans have essentially been tweeting since last night, channeling their inner Edmund Burke. 

Well, "it could have looked rude, but Biden made it look tough," argued Politico's Roger Simon. "By the end of the evening, Joltin' Joe had done real damage to his opponent."

As usual, the truth probably lies somewhere in the middle.

Ryan lied about unemployment. The congressman may have thought he would nail Biden by asking him if he knew that the jobless rate in Scranton, Pa. – Biden's hometown — was 10 percent, worse than the 8.5 percent when Biden and President Obama were sworn in. 

"That's how it's going all across America," Ryan said earnestly.

Biden: "You don't read the statistics. That's not how it's going. It's going down." 

Ryan, the wonky numbers man, seems to have missed the fact that the nation's unemployment rate fell last week to 7.8 percent, the lowest level in 44 months. Ryan walked into a trap of his own making, and had no response to Biden's counterattack. 

A few more:

Biden: Out of the loop on Libya? 
"We weren't told they wanted more security there. We did not know they wanted more security," he said when asked about the September 11 attack on our consulate in Benghazi. 

Biden, the former chairman of the Senate Foreign Relations Committee, apparently didn't read the unclassified cables released by a congressional committee that contradict last night's statement. 

Ryan: Misleading on green energy
Ryan rehashed Mitt Romney's claim that the Obama White House funneled $90 billion in green pork to campaign contributors and special interest groups. But Ryan's implication that all of the money went to failed companies like Solyndra simply isn't true. Yes, $16 billion — no small amount — did. But of the 28 companies that received loan guarantees, only three went bankrupt — better than Congress anticipated. Numbers guys like Romney and Ryan know, simply, that some investments work out and some don't. 

Biden: Misleading on the debt
Hand it to the veep, he can be very animated when he gets all worked up. "All of a sudden these guys are seized with concern about the debt they created," he cried last night. 

Biden is right that under the Bush administration, two wars, big tax cuts, and a costly expansion of Medicare caused the debt to surge, from $5.7 trillion in 2001 to $10.6 trillion in 2009. But that increase, over eight years, is less than the subsequent increase in the four years of the Obama presidency, which has seen debt grow an additional $5.5 trillion. About three-fifths of that is linked to the economic downturn that began on Bush's watch, but voters who simply look at these big numbers without nuance will see, correctly, that more red ink has been spilled on Obama's watch.

And the battle over small business taxes
Then there were issues when both men were both correct and misleading. On the complex matter of small business taxes, Ryan said the administration's proposed tax hikes on top earners would tax "about 53 percent" of small business income. Biden's retort: Only 3 percent of small businesses would be affected.  

Fact is, most small businesses don't pay corporate income tax rates, which are lower. Their income usually is listed on tax returns of the business owner, which is taxed at (higher) individual rates.

Biden's right that most small businesses don't report income of $250,000 and wouldn't be hit by higher rates that are set kick in next year. But Ryan's right that business income that would be exposed to higher individual rates is concentrated among the few businesses that would be effected. 

Complicated stuff, and I'm not sure viewers got it, but both men had a point.  

Fact checking aside, this was a great debate. Open, robust, and largely civil, with two competing versions of the future laid bare for voters to see. Much was left out over the course of the 90-minute clash, but the overall effect was one of transparency and dialogue. Such is the stuff of a vibrant democracy. 

So with election day just three weeks away, what does all this mean? Not much. As the table shows, VP debates tend to draw smaller audiences than their presidential brethren; they also tend to have little impact on the polls. One important exception: The year 2000, which our current race is increasingly being compared to.

 Sources: Nielsen, Gallup

(Provided by University of Virginia Center for Politics)

So even while last night's debate was terrific, it seems doubtful that it will change the campaign dynamic very much. 

The real goal of both men last night was to appeal to and shore up their base. This was particularly important for Biden, and he did it with gusto.

The stakes are now raised even higher for Tuesday's town hall-style debate between President Obama and Mitt Romney. The president is clearly preparing for this one. Other than dinner with a few winners of a campaign donation contest, he has no public appointments on his schedule today, and on Saturday, Sunday and Monday, he will hunker down in Williamsburg, Va. — to practice.