Madalyn Ruggiero/AP Photo

Vice President Joe Biden burst onto the scene of the 2012 presidential campaign today with a fiery speech before union workers in Ohio, portraying President Obama as a gutsy defender of the American auto industry who must be elected to a second term.

"I'm back, you're back and the industry's back," Biden told a cheering crowd at the United Auto Workers Local 12 in Toledo. "The president and I made a bet. A simple bet. We bet on you, we bet on American ingenuity. We bet on you, and we won."

Biden's vigorous defense of the 2009 government bailout of GM and Chrysler, the first of four issue-focused campaign speeches he plans to deliver over the next few weeks, underscored what Obama's campaign plans to make a major selling point and case study in "stark contrasts" with the Republican presidential field.

Mitt Romney "said that what we proposed 'is even worse than bankruptcy.' He said it would make GM 'the living dead,'" Biden said. "Newt Gingrich said it was 'a mistake.'"

"The guy I work for everyday, he didn't flinch," he added of Obama. "This is a man with steel in his spine."

Hailing the estimated one million auto industry jobs saved and more than 200,000 created since the government intervention, Biden doubled down on his declaration of victory while taking his rivals to task by name.

"He made the tough call and the verdict is in: President Obama was right, and they were dead wrong," Biden said, spurring perhaps the most spirited response to his address.

"And I say to Governor Romney: his prediction, Governor Romney's  prediction of the 'living dead,' we have now living proof," he added.

Biden for the first time directly rebutted Romney's claim that the industry could have survived without an infusion of taxpayer cash and that other automakers such as Ford could have picked up the slack in production if GM and Chrysler had gone down.  He even singled out Bain Capital, the investment firm Romney co-founded, for apparently not "lining up to lend anybody any money either."

"Mitt Romney, Rick Santorum, Newt Gingrich. These guys have a fundamentally different economic philosophy than we do," Biden said, framing the November election as a choice between competing visions rather than a referendum on the administration's record.

"If you give any one of these guys the keys to the White House, they will bankrupt the middle class again," Biden said.

This election is a "stark choice, but in my mind, not even a close call."

Romney campaign spokeswoman Andrea Saul responded to "attacks" on the former governor by invoking Biden's 2007 comment during the Democratic presidential primary that Obama was not ready to be president.

"More than four years later, it's clear that he was right," Saul said in an email. "Since taking office, President Obama has devastated the middle class by failing to live up to his promises of fixing unemployment, lowering gas prices, decreasing health care costs, and addressing the unsustainable federal debt."

This post has been updated from an earlier version.