WASHINGTON — 11 p.m. EDT

Under fire since Sunday for opening the door to payroll tax increases as part of a Social Security deal, John McCain escaped a policy full-nelson of his own creation, telling himself as much as his audience in Aurora, Colo., that he won’t raise taxes .

“I will not raise your taxes,” McCain said, looking down at his town hall notes propped before him. “I will not do it.”

But since McCain’s flank was exposed on the question of Social Security payroll taxes, McCain drove the anti-tax nail deeper into the town hall stage, invoking an apparent contrast with Barack Obama.

“He (Obama) wants to raise Social Security taxes,” McCain said, again looking down at his notes. “I want to fix the system without raising taxes.”

The crowd applauded and McCain appeared satisfied with the reaction. Perhaps even more satisfying came the reaction later Wednesday in Washington from The Club for Growth, a free-market, anti-tax bulldog that’s been harassing McCain on taxes since his campaign began.

“Today the Club for Growth thanked John McCain for reaffirming his opposition to increasing taxes, including Social Security taxes,” the Club said in a statement. “Although the Club for Growth expressed concern previously, John McCain’s comments today are a demonstration of his commitment to opposing higher taxes.”

And this, students of politics, would be what a physicist would recognize as action and reaction, or cause and effect. As the headline suggests, a gymnast might call this a forward flip coming out of a backward somersault. Whatever a gymnast might call it, an Olympic commentator would probably remark that it was a difficult, high-risk maneuver performed with “good amplitude.”

Thus McCain extracted himself, at least from the moment, from the skeptical maw of the Club and the acidic editorial writers at The Wall Street Journal who today scorched McCain for bungling the tax issue and predicting certain death for a GOP campaign that can’t decisively win the tax issue in hard economic times.

“If Mr. McCain can’t convince voters that he’s better on taxes than is a Democrat who says matter-of-factly that he wants to raise taxes, the Republican is going to lose in a rout,” the Journal wrote.

McCain started all of this, of course, when he told ABC’s “This Week” — when asked specifically if payroll tax increases were on the table — that “there is nothing that’s off the table. I have my positions, and I’ll articulate them. But nothing’s off the table.”

As garden variety analysis of future negotiations on a tough issue like Social Security, this answer makes perfect sense. As president, McCain meant to say, he would oppose higher payroll taxes but wouldn’t eliminate them from discussion because that could scuttle talks before they even began.

So what’s the problem?

Free-market Republicans are terrified, and with good reason, at way may happen to Congress on Election Day. They can see Republicans losing 20 seats in the House and at least 5 in the Senate. As a result, they don’t want any preemptive soft talk from McCain on taxes now. If he’s elected, they know McCain will face large and angry Democratic majorities more than willing to jam his “nothing is off the table” commitment right down his throat.

This and other misgivings were conveyed. McCain felt the pressure, saw he had stepped into it and flipped back as best he could.

And camp Obama couldn’t be happier.

Why?

Because now comes the other side of the pre-sharpened Democratic pincer on Social Security. Since Obama has already endorsed higher payroll taxes as part of his Social Security solvency plan (see: Hillary Clinton’s ads, mailers and robo calls about Obama’s “$1 trillion tax increase”), Obama was in no position to criticize McCain on the issue.

But now that McCain has walked it back, Obama can and Obama WILL, top aides tell me, hit McCain soon for adopting the same Social Security position as President Bush. Obama will say McCain has reverted to supporting voluntary private accounts while ruling out higher payroll taxes.

That means, Obama will say, McCain is now where Bush was in 2005, pushing private accounts but ignoring the hefty transition costs of converting Social Security from an entirely public, payroll-tax financed system to a partially private, partially public system weakened on the front end by lower payroll tax revenue.

We all remember how well that argument worked out for Bush when the economy, stock market and housing sector were far, far stronger than today. How do you think this argument will work now in the face of myriad downward economic pressures when Americans of all income categories are putting a premium on that which is safe, secure and dependable?

Yes, Social Security does not meet all of those criterion in the distant out years (starting about mid-century). But it meets them now. And if I’ve learned anything about Social Security debates since I started covering them in 1990, it’s that the here-and-now beats the sweet by-and-by every time.

When McCain opened up the tax can of worms on ABC on Sunday, he really dug his knife into the Social Security can as well. And if the Obama campaign has anything to say about it, McCain will smell more like Bush after opening these cans than he did before.