(CNN) - In his closely-watched visit to Iowa, Vice President Joe Biden delivered a campaign-style speech highlighting the Obama administration's accomplishments and painting himself with a fresh coat of the "Middle Class Joe" tint he so enthusiastically embraced in last year's presidential race.
Biden gave the keynote address at Sen. Tom Harkin's annual steak fry in Indianola for the first time since he appeared on the same stage in 2007 as a presidential candidate. Biden finished a distant fifth in the 2008 Iowa caucuses.
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Also on the stage Sunday was rising Democratic star Julian Castro, mayor of San Antonio and, like Biden, a potential presidential candidate.
Knowing his trip to Iowa - the first voting state in the presidential primary process - would spark a flurry of 2016 speculation, Biden opened up his remarks with a wink to the press.
"It's amazing when you come to speak at the steak fry, a whole lot of people seem to take notice. I don't know why the hell that is," Biden joked. "You've attracted the entire national press corps here."
'In Iowa, you're our friend, Joe'
The vice president lauded Harkin, who was holding his annual event for the 36th time. The longtime senator announced earlier this year he would not seek re-election in 2014, creating an open Senate race in Iowa for the first time in decades.
Before Biden took the podium, Harkin pointed to Biden's previous two bids for president and his numerous trips to the Hawkeye State.
"He spent so much time in Iowa, he has friends all over this state," Harkin said. "I'm sure he's an Iowan at heart."
The senator went to great lengths to describe Biden as someone who's "unpretentious" and "approachable," and who understands - down to the "marrow of his bones"– what it means to be middle class.
"Having known Joe for so many years, it's just hard not to call him Joe. So, Mr. Vice President, no disrespect, but to everyone here, to all of here in Iowa, you're our friend, Joe."
Biden in return praised Harkin for his work creating the Americans with Disabilities Act and changing "America's soul" on the issue.
A taste of what's to come?
The vice president has not said whether he'll make a third run for the Democratic presidential nomination. In addition to his unsuccessful bid in 2008, he ran for president in 1988.
"I can die a happy man never having been president of the United States of America. But it doesn't mean I won't run," Biden said in a July interview with GQ magazine.
If former Secretary of State Hillary Clinton decides to run for the White House again, polls indicate she would be considered the Democratic front-runner,with Biden a distant second.
But Biden continues to fan the flames of 2016 speculation when he travels Monday to South Carolina, which holds the first presidential primary in the South. He was also scheduled to host a fund-raiser for New Hampshire Gov. Maggie Hassan last month, but had to cancel when his son, Beau, needed to get medically evaluated in a hospital.
Asked about Biden and Clinton, President Barack Obama said it was too early to talk about the next White House race.
"We are tremendously lucky to have an incredible former secretary of state who couldn't have served me better, and an incredible vice president who couldn't be serving me better," Obama told ABC News in an interview that aired Sunday. "And I suspect if you asked both of 'em, they'd say, 'It's way premature to start talkin' about 2016'."
Biden frequently tied himself closely to the president in his remarks Sunday and emphasized the administration's work, including the health care law, an increase in student Pell grants, and the end of the war in Iraq. He was again unapologetic about speaking out for same-sex marriage last year ahead of the president, saying he "could not remain silent anymore."
But, he said, the president's two terms will most be judged by the health of the middle class.
"The measure of the success of our administration will be whether or not the middle class is growing," he said. Biden worked the rope line, meeting voters and taking photos, for nearly 40 minutes after his speech.
Speaking with Iowa reporters on Thursday, Harkin said its way "too early to speculate" about Biden's prospects, but he added "Joe Biden's always had good support among Iowa Democrats."
According to local reports, Harkin also said Biden "has a long history of working with Iowa Democrats, so I think that he would find - how should I phrase it? - fertile ground in Iowa if he should choose to run."
On Sunday, Harkin said the state has "endured" visits by a crop of potential Republican presidential candidates, including former Sen. Rick Santorum, Sen. Rand Paul and Sen. Ted Cruz, with "Governor 'Oops' Perry on his way."
"All I can say, folks, is the clown car is filling up pretty rapidly, early in the season," he joked.
A contrast in generations
Harkin said Castro and Biden represented the "new and the seasoned" that are needed in the Democratic Party.
In his speech, Castro talked about believing in the "blueprint" laid out by Obama and Biden, especially on health care, and emphasized the importance of education. He said his grandmother didn't get to finish school and had to work in the fields.
Saying this was his first real trip to Iowa, Castro said he looked out the window on the plane and took note of the "all of the fields, the green space."
"And I thought how proud she would have been that she had been picking crops and her grandson would be here where you guys pick a president of the United States," he said.
He encouraged Iowans to get out the vote for Rep. Bruce Braley of Iowa, the only announced Democratic candidate for next year's Senate race. Braley also has strong support from Harkin.
"I look forward to Election Night November 2016, I'll be in San Antonio, I'll probably have the TV on," he said. "I look forward to watching CNN and CBS and MSNBC and ABC. And I look forward to the moment when Brit Hume on Fox News turns to Bret Baier and says 'Bret, we're calling Iowa's electoral votes for the next president of the United States, the Democratic nominee for president."
– CNN Political Editor Paul Steinhauser contributed to this report.