ST. LOUIS – JOE Biden tiptoed out on stage last night wondering whether he’d face a lady pitifully out of her depth or the lipstick end of a pit bull.

He found out real fast.

Biden’s striped-pants Washington wonk talk ran into a regular American who looked like a lady, talked like a hockey mom and smacked him around like a cat playing with a mouse.

“Oh, man, it’s so obvious that I’m a Washington outsider and someone just not used to the way you guys operate,” Sarah Palin said in her arctic accent and a tone of utter disbelief.

Biden – the Senate’s reigning foreign-policy expert – had just given a long explanation for how he voted in favor of invading Iraq but didn’t really mean for President Bush to invade Iraq. And how he knew it would be a very long war and a very difficult war but now opposes the war because it’s been too long and too difficult.

As the debate began, Biden smiled broadly a lot, watching his opponent with open curiosity – as if unsure how exactly to handle this hissing mongoose without soiling his pin-striped suit.

So unsure that when he accidentally called her “Sarah Palin,” he corrected himself in a sweat: “Gov. Palin.”

By the time Biden figured out that he was debating nothing short of an icy china doll with a switch-blade, it was too late.

“Your plan is a white flag of surrender in Iraq,” she said fiercely. “And that is not what our troops need to hear today, that’s for sure.”

And while Palin talked like smiling – but p.o’d – hockey moms across America, Biden wooed the people with lines like: “Past is prologue.”

That’s one for the Congressional Record.

Or his oration on the role of the vice presidency and Dick Cheney’s performance therein: “The idea he’s part of the legislative branch is a bizarre notion invented by Cheney to aggrandize the power of a unitary executive.”

You tell her, Joe!

Palin’s got so much moxie, she actually went nuclear – or “nucular,” as she menacingly repeated over and over – on Barack Obama for his lack of foreign-policy experience.

Even when Biden made his strongest play of the night for women voters – choking up while reminding people that he was a single father after his wife died in a car crash – Palin didn’t let up.

“People aren’t looking for more of the same,” she responded – without halting for Biden to gather his composure. “And John McCain has been the consummate maverick in the Senate all these years.”

Charles Hurt is The Post’s DC Bureau Chief.churt@nypost.com

COMPLETE ELECTION 2008 COVERAGE