But more than three hours of public and private conversation did little to sway more than two dozen Jewish activists from across South Florida – many of them prominent Democratic donors – who strongly oppose the agreement. Even Biden's host, Rep. Debbie Wasserman Schultz (D-Fla.), said that she remains undecided about what to do.
Schultz, who is also chairman of the Democratic National Committee, heralded Biden as "Someone who quite literally we consider a 'mensch.' The term is so applicable to this man and I think there is universal agreement about that."
The Yiddish term "Mensch" means "a person of integrity of honor."
Biden's largely symbolic appearance came the day after President Obama secured enough votes in the Senate to preserve the nuclear deal despite fierce criticism from Republicans and some Democrats.
The vice president traveled to this predominantly Jewish community in Broward County, Fla., in part to give Schultz political cover as she faces intense pressure on the subject of Iran. Millions of dollars in television advertisements have aired across the state in support or opposition to the agreement. As the first female Jewish lawmaker from Florida and the DNC leader, all sides of the debate are closely scrutinizing every statement and meeting she holds. Several other Florida Democratic lawmakers remain undecided or say they will vote against the agreement.
In courting skeptical Democrats, Obama, Secretary of State John F. Kerry and other officials have sat for television interviews, given carefully-scripted speeches or reached out with private phone calls and letters. But no senior official had made an appearance quite like this one.
The exchange with Jewish activists was vintage Biden: Seated at the center of a dais, he gave a long-winded, sinuous presentation that bore a resemblance to floor speeches or committee-room statements he delivered as a senator. While the eyes of some attendees glazed over, he mentioned his involvement reviewing the SALT and START nuclear treaties with the Soviet Union and made passing reference to "Poroshenko," "Bibi," "Dilma" and "Xi" -- the leaders of Ukraine, Israel, Brazil and China.
"Guys – last point," he said, before catching himself. "I've said that three times."
The discourse grew emotional just once, as he reached into his suit pocket and pulled out a white card listing the number of U.S. military casualties in Iraq and Afghanistan and the miles he's traveled in the last seven years.
Biden explained that he carries the card "Because every life matters, because of my son," as he choked back tears.
Beau Biden, 46, died in May of brain cancer. The former Delaware attorney general was also a National Guard major.
"I’ve traveled, as of today, 992,894 miles for the president," he added. "I’ve met with virtually every major leader in the world. I know these guys. I know them better than anybody in the administration because I’ve been hanging around so long."
His son's death sparked talk of a possible Joe Biden presidential campaign, especially after news reports revealed that before dying, Beau Biden encouraged his father to run. Close aides and friends say that the vice president is considering a campaign, but is most concerned with whether his still-grieving family could handle the pressure.
If he launches a campaign, Thursday's event was an early reminder to would-be supporters of Biden's deep knowledge of foreign affairs and support for Israel. Repeatedly he mentioned his friend, Israeli Prime Minister Benjamin Netanyahu, saying that despite disagreements over Iran, their friendship would endure.
"I take a back seat to no one" when it comes to defending Israel, he said. "I may not be Jewish, but I was raised by a righteous Christian and my entire – one of the rationales for getting engaged as a 20-year-old kid and from the beginning has been my view, my view, not only of a moral obligation I have, but the strategic importance of the state of Israel. Were there no Israel, we’d have to invent one."
Reporters were escorted out before Biden took questions from the attendees, per Schultz's previously stated "ground rules" that the question-and-answer session be private.
"Take out your cellphone and switch it to the off position," she instructed attendees, asking them not to share details of the private meeting with reporters.
Not everyone in the room obliged.
Over the course of the more than two-hour meeting, "Maybe I went from 80 percent against to 56 percent," said Barry Wilen, an attorney and community center board member. But even if the meeting had gone longer, "I'd still be above 51 percent."
"Whatever the opposite word for ‘toxic,’ it was that," said Baruch "Bruce" Levy of Weston, Fla. "It was a frank, open, honest, informative conversation. Passionate, and I gotta tell you – I was very impressed with his knowledge, his passion, his ability to explain things and present them from a little wider perspective."
Levy, like many others in the room, is opposed to the agreement. "But the main thing to remember is that this is not a black and white issue," he said. "If you keep that in the back of your mind as you analyze it, you realize that either way, the sky will not fall whether it passes or not."
Andrew Weinstein, an attorney and prominent Democratic donor from Coral Springs, Fla., said that Biden never mentioned and wasn't asked about a potential White House campaign.
"The questions were friendly and I think they were reflective of the respect the vice president has in the Jewish community," he said.
Over the weekend, Schultz prevented consideration of a resolution at the DNC’s summer meeting that praised Obama and offered backing for the nuclear agreement with Iran. Several party activists faulted Schultz for blocking attempts to consider the resolution and as a fallback, party elders co-signed a letter of support for Obama and the Iran agreement.
On Thursday, she told reporters that party rules didn't allow for the resolution to be considered the way it was introduced.
Pressed about her motivations for blocking consideration of the resolution, Schultz shot back: "You want me to say that my making sure that the DNC was following our rules should be read other than that way? ... Should I have violated our rules to ensure that proponents of the deal think I'm for it? I have to follow the rules, that's the bottom line."
Despite Biden's unique appearance on her behalf, Schultz told reporters that she still has more information to compile. On Thursday afternoon, she planned to speak with the German ambassador to the United States and two Harvard nuclear experts.
"Then I'm going to spend a little time – having pulled together all this information [and] opinion – and sort of consult my conscience and make a decision," she said.