By Michael Barone - October 8, 2012

Wednesday night's presidential debate in which Mitt Romney shellacked Barack Obama attracted the biggest audience since the debate between Jimmy Carter and Ronald Reagan seven days before the 1980 election.

About 70 million Americans watched, a little more than half the 131 million voter turnout in 2008. That's an estimate, because the ratings companies don't count those watching on C-SPAN, PBS or the Internet.

Did the debates matter? The first state polls, conducted by Rasmussen and We Ask America on Thursday night, suggest the answer is yes.

Rasmussen reported that Romney was down 1 point in Ohio. We Ask America had him up 1 there.

Rasmussen had Romney up 1 in Virginia. We Ask America had him up 3. And in Florida We Ask America had Romney up 3.

These states are important because the Obama campaign has spent millions on anti-Romney ads there, to build a firewall blocking Romney from getting to a 270-vote majority in the Electoral College.

The arithmetic is fairly simple. The 28 states plus the District of Columbia and one Nebraska congressional district Obama carried in 2008 have 359 electoral votes this year. Subtract Indiana, which has fallen off the target list, and the Nebraska district, and he's down to 347.

Subtract also the 15 electoral votes of North Carolina, which Team Obama hoped to contest but where it hasn't been spending much money lately, and you're down to 332.

Obama's next three closest states were Florida, Ohio and Virginia, which together have 60 electoral votes. In every other state he carried, he ran ahead of his 53 percent share of the national vote.

Up to the debate, the tri-state strategy seemed to be working. Obama carried Florida by 3 points in 2008, and the Realclearpolitics.com average of recent polls going into the debate showed him up 2 there.

Obama carried Ohio by 5 points, and pre-debate polling had him up 5 (I've rounded off the percentages and rounded .5s to the lower integer). Obama carried Virginia by 7 points, and pre-debate polling had him up 3.

In contrast, pre-debate polls had Obama lagging further behind his 2008 showing in five other target states -- Colorado, Iowa, New Hampshire, Nevada and Wisconsin.

Not to worry, Obama strategists said. If we hold Florida, Ohio and Virginia, we've got 332 electoral votes, way over 270. We can afford to lose the 35 electoral votes in those other five states.

But what if the firewall doesn't hold? If the big three go for Romney, Obama is down to 272. If he loses one more state, he can join Al Gore on Current TV.

The Obama strategy didn't count on a debate performance like the one 70 million Americans watched Wednesday night.

As his dazed spin team pointed out, other incumbent presidents have stumbled in their first debates. But none ever had an instant poll report, as CNN's did, that the challenger won by a margin of 67 to 25 percent.

The fact is that for all his professions of bipartisan amity, Obama cannot bear to listen to tough questions or well made counterarguments. He certainly hasn't had to in the 200-plus fundraisers he's attended.

On the split screen, we saw the same expression of irritation -- as if he smelled something really bad -- as we did when he faced tough questions from Fox News' Bret Baier, when he had to listen to Paul Ryan demolish his health care plan at the Blair House summit, when he was probed on his broken immigration promise by interviewers on Univision.

What we didn't see is the Obama who is supposedly fascinated by the details of public policy. Sans teleprompter, he repeated the talking points of his television ads and, when Romney responded sharply, he had nothing to fall back on.

We saw the president who found it fitting to jet off to campaign in Las Vegas the day after the first murder of a U.S. ambassador in 33 years.

As you read this, you have more polling information than I do as I write. It's possible that the trend suggested by the Rasmussen and We Ask America results in Florida, Ohio and Virginia will not be confirmed by other polls. And there's a whole month till the election.

Obama will surely perform better in his next two debates. Romney may not perform as well. But the first numbers suggest the firewall may be crumbling. We'll see if it holds.