Joe Biden knew Lloyd Bentsen.

Lloyd Bentsen was a friend of Joe Biden’s.

And the vice president made full use of his old Senate colleague’s 1988 debate playbook, shaking his head and scoffing pityingly at Representative Paul D. Ryan, trying to paint his opponent as a latter-day Dan Quayle.

Mr. Ryan was no Dan Quayle, but he did make the mistake of mentioning John F. Kennedy in an argument over whether tax cuts recharge the economy. Mr. Biden flashed a Cheshire Cat grin and said to Ryan, after waiting a beat to let the moment sink in, “So, now you’re Jack Kennedy?”

The vice presidential debate on Tuesday was supposed to be a reboot for the Obama campaign after the president’s dismal performance at his debate with the Republican nominee for president, Mitt Romney, last week. Mr. Biden, clearly delighted to come to President Obama’s rescue, relished his role, addressing his opponent as “my friend” but dismissing his arguments as “malarkey.” He laughed at Mr. Ryan’s remarks so often and so heartily that at times he seemed like a guest at a comedy club roast, not a vice president debating the fate of the nation with his opponent.

It was a sharp and spirited debate, with both candidates delivering some lacerating blows, but Mr. Ryan at times seemed disconcerted by the sheer blowhard intensity Mr. Biden brought to the night. Mr. Ryan tried to be respectful, listening to the vice president with a tilted head, choirboy smile and puppy-dog eyes, but he showed his irritation when Mr. Biden kept interrupting to attack his policy on Medicare. “I know you’re under duress,” he told the vice president, prompting another belly laugh.