And while Biden received applause at his meeting with House Democrats on Tuesday, members said that his pitch was mostly policy-focused and didn't appear to have immediately swayed many lawmakers into the White House's camp. "The vice president made as convincing an argument as he can make, but I think there's still a lot of questions to be answered," said Rep. Steve Israel. "I've been skeptical from the beginning of this. I'm still skeptical. "¦ He did as good a job as he could do under the circumstances."
But Biden's campaign is far from over. Many members said that while they'd heard from the vice president and other members of the administration, they had a lot more reading and research to do before they make a decision and they expect to have many more questions for Biden and the White House before then.
Sen. Brian Schatz, who said he has not yet heard from Biden personally, praised the vice president as "the perfect point-person for this," noting: "He's persuasive and he has knowledge. He's got great bipartisan relationships and he has impeccable credentials when it comes to support for Israel and knowledge of the security needs in the region."
But, Schatz added, Biden isn't alone in his lobbying campaign.
A small group of Senate Democrats earned invitations to the White House on Wednesday afternoon for a 90-minute briefing from staff on the deal, including Sens. Al Franken, Martin Heinrich, and Joe Manchin. Sen. Tammy Baldwin was also invited to the meeting, but had a scheduling conflict.
Heinrich and Manchin both sit on the Senate Armed Services Committee, which will hold hearings on the deal. "They went over everything and explained to us how we got to where we are today, and everything they're doing," Manchin said.
The West Virginia Democrat said he appreciates the White House's outreach, calling the briefing "informative.
"It helps us because I'm looking for a pathway to basically have any stability, any peace, whatsoever," Manchin said.
Secretary of State John Kerry is also expected to be instrumental in securing support for the deal he helped to craft in Vienna. Kerry will testify before the House Foreign Affairs Committee next week. Kerry will also appear before the Senate Foreign Relations panel next Thursday, along with Moniz and Treasury Secretary Jacob Lew.
Kerry has been hitting the phones since early Tuesday morning, along with Energy Secretary Ernest Moniz, National Security Adviser Susan Rice, Deputy Secretary of State Tony Blinken, White House Chief of Staff Denis McDonough, and other administration officials and Cabinet members.
Sen. Tim Kaine said he'd spoken with Blinken in an early Tuesday morning phone call, as administration officials reached out to some senators to brief them on the plan.
"I had a long talk with Tony, which I really appreciated," Kaine said. "He answered a lot of my questions, but I had not read the document when I had the conversation with him, so now that he's kind of given me his pitch and answered questions, now I'm reading the document to try to reach my own conclusions."