Vice President Joe Biden speaks in Council Bluffs, Iowa, on Thursday. (Nati Harnik/AP)

Vice President Biden was in attack-dog mode Thursday afternoon at a campaign event in Council Bluffs, Iowa, where he took aim at both Mitt Romney and his running mate, Paul Ryan, at his first rally following the presidential debate.

Ryan, he told the crowd, is a “smart guy” when it comes to the federal budget — “I just fundamentally disagree with everything he has to say about it.”

Of the GOP ticket, Biden said that “these guys will not support one single idea to reduce the debt if it raises one single dollar on people making one million dollars or more — that’s a fact — and [Romney] reasserted it last night.”

“So much for their concern. So much for this urgency,” he added.

Biden’s remarks came after what was widely seen as a strong performance by Romney at the first presidential debate Wednesday night. Post-debate polls showed that most viewers believe the GOP candidate won the face-off with a more subdued President Obama. The president and his campaign tried to recover Thursday by arguing that Romney’s debate answers were misleading.

Taking another stab at a line he bungled earlier this week, Biden said of Republicans, “Their policies put the middle class in an incredibly deep hole, which we’ve been helping them climb out of over the last four years.”

And he argued that, as if it weren’t “bad enough” that Romney has declined to release more information about his tax returns, “Now he won’t even release the details of what he plans on doing about your taxes!”

Biden also mocked Ryan and other Republicans for mentioning the middle class at August’s GOP convention in Tampa “more than I heard the Republican congressman use it over the last four years.”

“They discovered the middle class!” Biden said to laughs. “It’s like, ‘My God, there it is! It’s out there! There is a middle class! We are concerned about it! We share your values! Whoa! God, I didn’t see you there, I don’t know how I could’ve overlooked you these last eight years. You’re right in front of me. It was amazing.’”

Seizing on Romney’s performance at Wednesday’s first presidential debate in Denver, Biden told the crowd that the GOP presidential nominee had “quadrupled down” on his opposition to new revenue in any comprehensive debt-reduction plan.

“No reasonable person out there — none of the economists out there who are taken seriously — think you can get hold of this national debt unless you do two things: make serious cuts in spending and throttle the hemorrhaging of tax cuts for the super-wealthy,” Biden said.

At times, Biden lowered his voice as he paraphrased the points made by the Republican ticket, such as when he took aim at Romney’s statement in Wednesday’s debate that he opposes cutting education funding.

“Yo! That came as a real surprise to your Republican colleagues in the House, man,” Biden said, seeking to tie Romney to the cuts included in the House GOP budget blueprint.

And, in contrast to Obama at Wednesday’s debate, Biden took aim at Romney’s closed-door fundraiser remark that he’s not concerned about trying to win the support of the “47 percent” of Americans who pay no income taxes and who he said view themselves as victims.

“For real, think about it — describing almost half of the population as not wanting to take personal responsibility,” Biden said.

Republicans hit back at Biden by seizing on his statement at the rally that he and Obama would let the Bush-era tax cuts expire for the wealthy.

“Fresh off admitting that America’s middle class has been ‘buried’ over the last four years, Vice President Biden went a step further today and fully embraced the president’s job-killing tax increases,” Romney campaign spokesman Ryan Williams said. “The choice facing Americans in this election gets clearer every day. We can either have four more years like the last four, with the same policies that have resulted in high unemployment and falling incomes, or we can elect Mitt Romney – who will lead us to a real recovery with more jobs and higher take-home pay.”

Biden had told the Iowa crowd, “You know the phrase they always use? ‘Obama and Biden want to raise taxes by a trillion dollars.’ Guess what? Yes we do, in one regard. We want to let that trillion-dollar tax cut expire, so the middle class doesn’t have to bear the burden of all that money going to the super-wealthy. That’s not a tax raise, that’s called fairness where I come from.”