Adam Green, co-director of the Progressive Change Campaign Committee, left it at this: "Joe Biden has had a great career in public service."
After the interview concluded, Green e-mailed to say that his co-director, Stephanie Taylor, has this to say about a Biden run: "That would be funny," Taylor said.
Democratic pollster Margie Omero said Democrats Biden and Clinton aren't the only two who can appeal to Democratic voters.
The party has "a really strong bench of candidates that people are excited about that have progressive appeal."
She included Maryland Gov. Martin O'Malley, saying he has "quietly and consistently" built a strong record of good schools and good economy in Maryland.
Interestingly, in this informal survey of half a dozen Democratic operatives and one political science professor, people mentioned O'Malley most often than any other possible contender, including Biden, but their reaction was far more muted.
Manley said the "jury is out" and Abramowitz mused, "I just don't know what kind of candidate he'd be."
Green called O'Malley "a blank slate."
O'Malley is laying the groundwork for a run in the event Clinton doesn't, a source close to the governor told CNN.
O'Malley amplified 2016 speculation when he told the Washington Post last week that he can't wait for the former first lady and secretary of state to make a decision.
The first-term Massachusetts senator would have even less experience in public office than Obama when he ran in 2008.
But Democrats have a high opinion of the former Harvard professor whose advocacy paved the way for the Consumer Federal Protection Bureau.
Former Obama aide Bill Burton said Warren was one of a handful of "impressive" Democrats who could fill the bill should Clinton stay out.
Cardona said Warren has to be "put on any list."
The progressives love her for her populist agenda. Green said Warren is "the north star" of the Democratic Party.
New York Sen. Kirsten Gillibrand's name also came up as a potential contender. But Cardona said she would have to get over her lack of name recognition, which she said is relatively easy to do.
Manley, however, said it's "too soon" for New York Sen. Kirsten Gillibrand. She should show her campaigning and fundraising capabilities as head of the Democrat's Senate campaign arm.
The New York governor received the most negative response from respondents, if he was mentioned at all.
Manley said Andrew Cuomo should "stick to being the governor of New York."
Green said he represents the Democratic Party from the 90s and would not fit in well with today's voters, adding that he "pays lip service" to progressives.
More on the bench?