With Joe Biden in the lead…a few whispers for Hillary and Mike Bloomberg?…

When a half-dozen Democratic donors gathered at the Whitby Hotel in Manhattan last week, the dinner began with a discussion of which presidential candidates the contributors liked. But as conversations among influential Democrats often go these days, the meeting quickly evolved into a discussion of who was not in the race — but could be lured in.

Would Hillary Clinton get in, the contributors wondered, and how about Michael R. Bloomberg, the former New York mayor? One person even mused whether Michelle Obama would consider a late entry, according to two people who attended the event, which was hosted by the progressive group American Bridge.

It’s that time of the election season for Democrats.

“Since the last debate, just anecdotally, I’ve had five or six people ask me: ‘Is there anybody else?’” said Leah Daughtry, a longtime Democrat who has run two of the party’s recent conventions.

With doubts rising about former Vice President Joseph R. Biden’s ability to finance a multistate primary campaign, persistent questions about Senator Elizabeth Warren’s viability in the general election and skepticism that Mayor Pete Buttigieg, of South Bend, Ind., can broaden his appeal beyond white voters, Democratic leaders are engaging in a familiar rite: fretting about who is in the race and longing for a white knight to enter the contest at the last minute.