CHARLOTTE, N.C.- Vice President Biden, who has become a punch line for Republicans after a series of verbal gaffes and plunging approval ratings, sought to revamp his public image with a passionate but meandering speech at the Democratic convention.

Biden acted as the chief defender of President Obama, saying the president had made a series of tough calls, ranging from the bailout of the auto industry to the killing of Osama bin Laden, that proved his mettle.

"Folks, I've watched him. He never wavers," Biden said. "He always steps up. And because of the decisions he's made, and the incredible strength of the American people, America has turned the corner."

But Biden's speech was not free of the bumbles and perplexing language that have dogged his public profile. At one point he indicated his long-dead father admired Obama, before correcting himself and saying he would have admired the president. And in trying to reach a rhetorical high point in his speech, he said, "Never ever, it never makes sense to bet against the American people."

(Watch highlights from Biden's speech above, or view his full remarks below)

Biden's primary role was to frame Republican challenger Mitt Romney as aloof to the concerns of middle-class Americans, while contrasting his own blue-collar upbringing with that of the wealthy former governor of Massachusetts.

"We both had a pretty good idea what these families were going through -- in part because our own families had gone through similar struggles," Biden said of the Democratic ticket. "A job is about a lot more than a paycheck. It's about dignity. It's about respect."

(Read the full text of Biden's speech)

Traditionally, the vice president receives the primary speaking role during one night of the convention, but the Obama campaign opted to have Biden yield the spotlight to the president.

At times, the vice president has been more of a liability for Obama than an asset.

According to a recent Pew poll, 40 percent of respondents said that "idiot" was the first word that came to mind when thinking of Biden. While Biden has received praise for his authenticity on the campaign trail, Obama can ill-afford to have his No. 2 look like a court jester heading into November.

Biden landed in hot water when he told a largely black audience that Romney wanted to "put y'all back in chains," prompting charges of race baiting by the GOP -- in the latest example of Biden going wildly off message.

(Watch video clips of some of Biden's more notable gaffes.)

That gaffe ignited a fresh round of criticism from some Democrats, who said Obama should ditch Biden for somebody more polished, such as Secretary of State Hillary Clinton.

But on Thursday the vice president sought to reach the white, working-class voters in states like Ohio and Pennsylvania by focusing on jobs and security -- sometimes in the same extended thought. "This man has courage in his soul, compassion in his heart and steel in his spine," he said of Obama. "And because of all the actions that he took, because of the calls that he made, and because of the grit and determination of American workers, and the unparalleled bravery of our special forces, we can now finally say, Osama bin Laden is dead and General Motors is alive."

Biden said Romney isn't a "bad guy" but operates under a different set of principles than those motivating Obama, the former inner-city community organizer.

"Folks, the Bain way may bring your firm the highest profit, but it's not the way to lead your country from its highest office," Biden said.