Until last night, the conventional wisdom about John McCain was that he bestrode “town hall” meetings like a conqueror, that he was loose and spontaneous and likable and witty. And so he usually was. The difference this time, however, was that he had to share the stage with Barack Obama, and at the end of 90 minutes, McCain was no longer the master of his domain.

McCain’s performance was perfectly serviceable, but that wasn’t good enough. Given the crystallizing fundamentals of this campaign, he needed to contrive a spectacular moment of contrast during the second presidential debate, something that would elevate him and diminish Obama, something that would change the basic story line. He failed to do that. As such, he failed to reverse his apparently waning political prospects.

There was nothing particularly memorable about this debate – both candidates spent much of their time repeating old arguments, and trading familiar ripostes – and that alone helps Obama. He was ahead before the debate began, as evidenced by all the national and state battleground polls, and so he remains.

As I mentioned here on Monday, voters at this point seem poised to oust the Republicans from the White House, seeking only to be reassured that Obama is not an unacceptable risk. The “town hall” debate has apparently reassured them further. McCain works the room just fine when he’s alone, but apparently comes off second best when Obama is around.

So say the voters, anyway. An overnight poll, by CNN and the Opinion Research Corp., has delivered a strong verdict: 54 percent of debate-watchers said that Obama won; only 30 percent chose McCain. Among those who identified themselves as independents, the spread was 54 to 28 percent. On the question of which candidate seemed more likable, the debate-watchers chose Obama by 65 to 28 percent. McCain fans would probably attribute that result to Obama’s “celebrity,” but this stat is less easily dismissed: 54 percent of debate-watchers said that Obama came off as the “stronger leader” with only 43 percent choosing McCain.

It’s impossible to know which debate exchanges triggered those verdicts. But whatever it is that McCain is doing, it’s clearly not working. His familiar attack lines don’t seem to be moving many votes. Tagging Obama as a “liberal” who “wants to raise taxes” – that isn’t working.  Claiming that Obama has already voted “94 times” to raise taxes isn’t working. Claiming that Obama was in the pocket of Fannie Mae and Freddie Mac – that isn’t working.

It should be noted, yet again, that many of McCain’s attack lines are misleading or worse. Indeed, it’s tragic that a politician who talks to much about “honor” would so often dishonor himself by reciting the same lies over and over. But such is the case when defeat looms and desperation takes hold. I’ve deconstructed the “94 times” lie before, and won’t take up space doing it again. The line about Obama wanting to “raise taxes” is a rank distortion, since Obama mainly wants to cancel the Bush tax cuts for people making $250,000 or more.

As for the line about Obama being a lefty ideologue, here’s what McCain said last night: “Go to some of these organizations that are the watchdogs of what we do, like the Citizens Against Government Waste or the National Taxpayers Union…and you know what you’ll find? (Obama has) the most liberal, big-spending record in the United States Senate.” But McCain lied. When you actually check out the National Taxpayers Union, you discover that 12 senators received worse ratings than Obama in 2007, and 31 senators received worse ratings in 2006. And when you check out Citizens Against Government Waste, you find that 47 senators received worse ratings than Obama in 2007…including – and this is my favorite factoid – the senator from Connecticut and close McCain buddy, Joseph I. Lieberman.

McCain’s efforts to tie Obama to Fannie and Freddie were particularly misleading. He said at one point that Obama is the second-highest recipient of Fannie and Freddie campaign donations of any senator “in history.” That’s basically true (the donations total $126,349), although, by some measurements, Obama ranks third. But what McCain forgot to mention was that his own campaign manager, Rick Davis, was on the hook to Fannie and Freddie for five years, that Davis was paid nearly $2 million to lobby against stricter regulations, and that Davis’ lobbying firm was receiving $15,000 a month from Freddie until this August.

But I digress. Most swing voters are not going to do the fact-checking spadework. McCain is imperiled not because these voters doubt the veracity of his charges, but because they’re inclined to simply tune out his charges. His biggest problem is not his credibility, but the party label he shares with George W. Bush.

The economy is in the tank for many reasons, but most voters know by now that Bush inherited a healthy budget surplus and that he has since driven us deep into deficit ($438 billion; Obama rounded it up last night to half a trillion). To many voters, that looks a lot like serious fiscal mismanagement. Combine that with the common perception of the Republicans as the party of business, free markets, and deregulation…and then suddenly McCain’s supposed “town hall” prowess seems an illusion. And his railings against congressional earmarks (as he did again last night) strike many voters as off point, even if they don’t actually know that earmarks are a mere one percent of all federal spending.

McCain is also stuck with the Bush brand on Iraq. Most Americans have long concluded that the U.S. invasion was a mistake, so Obama did himself no harm last night by reminding Americans that McCain had urged the invasion. After McCain told a questioner that Obama "does not understand our national security challenges," Obama fired back: "I don't understand how we ended up invading a country that had nothing to do with 9/11, while Osama Bin Laden and Al Qaeda are setting up base camps and safe havens to train terrorists to attack us. That was Senator McCain's judgment and it was the wrong judgment. When Senator McCain was cheerleading the president to go into Iraq, he suggested it was going to be quick and easy, we'd be greeted as liberators. That was the wrong judgment, and it's been costly to us," in terms of the strain on the domestic economy.

But perhaps the moment that best epitomized McCain's plight occurred early in the evening. Clearly hoping to get some kind of traction on the economy, he surprised everybody by announcing that, as president, he would order the U.S. treasury secretary to "buy up the bad home loan mortgages in America," and replace them with more affordable loans. The very notion that a Republican candidate would propose such a big-government solution...what better proof can there be that the GOP free-market ethos is out of step with the '08 zeitgeist? I would bet, however, that many GOP conservative voters were aghast to hear McCain propose a new burden on taxpayers, although, if it's any consolation to them, McCain characteristically failed to fill in the nuances of his proposal during the remaining 80 minutes. After all, he has already admitted that economics aren't his strong suit.

The public seems to agree with that admission. A post-debate poll, sponsored by CBS News and Knowledge Networks, reported that 68 percent of uncommitted voters trust Obama to make the right decisions on the economy, while 31 percent do not. By contrast, only 48 percent trust McCain on this policy front, while 51 percent do not.

Richard Viguerie, one of the founders of the modern conservative movement, offered this assessment when the debate ended: “For John McCain, the opportunities to win this election are dwindling down to a precious few.” That sounds about right.