There have been a flurry of recent stories in The New York Times, The Washington Post and other outlets about influential Democratic powerbrokers casting about for new 2020 candidates, apparently due to doubt about the strength of the current field. And in a related development, former New York City Mayor Michael Bloomberg, former U.S. Attorney General Eric Holder and former Massachusetts Gov. Deval Patrick are all reportedly considering entering the race, even as they would face long odds against winning the nomination.

Can’t the party establishment just live with one of the candidates who are already running? After all, the Democratic field is getting smaller, but it’s still huge, with 16 “major” candidates. And the party’s voters like the candidates just fine. A Pew Research Center survey conducted in July found record-high levels of enthusiasm about the field among Democratic voters, matched only by their excitement in 2008 when Hillary Clinton and Barack Obama were running. A Huffpost/YouGov survey from last month found that 83 percent of Democrats were satisfied with the party’s candidates.

So … what’s going on? Why are the party pooh-bahs so nervous?

It’s difficult to provide a definitive answer to this question, in large part because “Democratic donors” and “the Democratic establishment” are large, nebulous groups. We don’t have a formal poll testing the views of the “establishment,” for example. Plus, news organizations tend to be more likely to write stories with the theme “people are worried” than “everything is fine,” so you should be somewhat skeptical of how representative these stories are of opinions overall.

That said, my own interviews and conversations with elite Democrats and those who have talked to other reporters do suggest that some members of the establishment are nervous. So this is view is out there, even if I can’t quite tell you how pervasive it is. But however widespread the feeling is, I don’t think it’s too difficult to understand. Here are three explanations that cropped up in my reporting, ordered from most to least important (at least in my view):

An unorthodox group of front-runners

If you are a major Democratic donor or a Democratic National Committee member, you likely were a strong supporter of at least one of the last two Democratic presidents, Bill Clinton and Barack Obama. You want to win the general election, and you’re looking for what’s worked in the past. In November 1991, Clinton was 45 years old and had served as Arkansas’s governor for more than a decade. In November 2007, Barack Obama was 46 years old and had served in the U.S. Senate for two years. Ideologically, both positioned themselves as center-left (as opposed to more openly liberal) during their campaigns.

I think if one of the candidates at the top of the polls was or had been a governor or senator, was between the ages of, roughly, 40 and 70, and was not considered either too liberal or too conservative by many in the party, then the party’s elites would not be casting about for someone else. Instead, from the point of view of these party elites, the leading contenders include …

Fellow FiveThirtyEight contributor Julia Azari, a Marquette University professor, argues in an essay in the book “The Making of the Presidential Candidates 2020” that there is a deep tension right now in the Democratic Party between “risk aversion and orientation toward the status quo” on the one hand and an increasingly powerful bloc pushing for more progressive ideas on the other. That status-quo-oriented group seems to be the one looking for alternatives.

Most key figures in the Democratic Party haven’t endorsed anyone yet. But among the endorsements we do have, you can see these elite preferences in action. Cory Booker (sitting senator, 50 years old, not as left as Sanders and Warren) is right behind Warren in number of endorsements so far, and Kamala Harris (sitting senator, 55 years old, not as left as Sanders and Warren) is well ahead of Warren in endorsements. Both Booker and Harris are also leading Sanders, despite clearly trailing Warren and Sanders in the polls. If Harris and, especially, Booker (because he is a man and would therefore be considered a safer choice by some Democrats) were polling at the level Warren is, my guess is that they would be getting a flood of endorsements and lots more buzz.

In short, party establishment figures think they know what a great White House candidate looks like — and they aren’t sure they’ve seen one yet. One longtime D.C.-based Democratic operative I talked to referred to “head-scratching” among the party’s establishment, “wondering why these super-talented candidates are making some really dumb mistakes.” Those mistakes, according to this strategist, included Biden’s campaign spending more than it raised from July to September, Buttigieg’s lack of succcessful outreach to black voters, Harris’s struggles to come up with a clear message and Warren fully embracing “Medicare for All.”

Worry about Warren

Party establishment types that I have talked to see a scenario in which Warren wins Iowa, where she is polling well, and New Hampshire, where voters are fairly familiar with the Massachusetts senator. With those two early wins, she becomes more popular, particularly with nonwhite voters, and basically sweeps to the nomination. This is basically what happened in 2004 with John Kerry and similar to what happened with Obama in 2008 (he came in a close second in New Hampshire). The party establishment types may be wrong in predicting that outcome, but they are speaking from their own recent experiences.

“If she wins Iowa, this whole thing could be over,” a DNC member told me.

And the prospect of a Warren nomination has some party insiders worried. Establishment Democrats often cast Warren as a bad general election candidate, but many of them simply don’t want her to be president — she has fairly aggressive policy plans to take on elite, wealthy Democrats (and Republicans). Bloomberg’s aides are essentially telegraphing a plan to stop Warren: If Biden struggles in the early states, the former New York mayor will enter the race on Super Tuesday, running as the moderate alternative to Warren instead of Biden.

Biden’s problems, according to the party elites I spoke with, boil down to a fear he won’t be able to stop Warren, and that he’s vulnerable largely because he is not clearly leading in Iowa or New Hampshire.

“Buttigieg, Warren and Sanders have created national movements around their candidacies; Biden absolutely has the potential to do that, but he hasn’t so far,” said Robert Zimmerman, a New Yorker who is both a longtime party donor and a DNC member.

I think Democratic elites are overly pessimistic about Biden’s candidacy. The former vice president, according to the polls, is a clear front-runner in the primary and polls well against Trump in the general election. It’s not even guaranteed that he will lose Iowa or New Hampshire, but even if he does, polling suggests Biden will still be in a strong position in Nevada and South Carolina because he does better with nonwhite voters.

But Democratic elites have never been enthralled with Biden as a potential general election candidate or president. When Biden considered a White House run in 2016, for instance, Barack Obama and his aides weren’t exactly encouraging — in fact, some of their moves bordered on discouraging. In all, Biden ran for president two times, in 1988 and 2008, and flirted with runs four other times, in 1980, 1984, 2004 and 2016. The party elite didn’t rally behind him in any of those races — and they aren’t doing so now.

Elites have basically given up on lower-tier candidates

You might be thinking, particularly regarding the nascent Holder and Patrick campaigns, what’s wrong with Cory Booker and Kamala Harris, the two center-left black candidates already in the race? Why doesn’t the establishment just unify behind one of the people who isn’t in the top four but who already has a campaign infrastructure and would be a fairly conventional party nominee? What about Amy Klobuchar or Julián Castro?

Donors and party elites don’t see these candidates as viable, because they’re so far down in the polls. (There is a bit of a contradiction here, in that the donors are pessimistic about Biden despite his strong polling but down on the other candidates because of their weak polling.)

There have been public reports about Harris’s campaign donors, in particular, starting to think that she is no longer a viable candidate. And even as Democratic establishment types emphasize the importance of nominating an electable candidate, they are making little effort to boost Gov. Steve Bullock of Montana or Sen. Amy Klobuchar of Minnesota, both of whom have won in areas where Trump was strong in 2016. (Trump won Montana and many rural counties in Minnesota that Klobuchar carried in 2018.)

“I think the problem isn’t so much that there is no one good in the field, but that it seems harder to get Harris or Booker to move to the front of the pack than it is to get an unknown to jump in and maybe immediately get attention and move to the front,” said Hans Noel, a Georgetown University professor and expert on dynamics within the two parties.

He added, “I don’t have any reporting on this, but I wouldn’t be surprised to learn that Patrick or Holder had been discouraged from running because someone like Booker or Harris or Castro was already in the field. Now that they [Booker, Harris, Castro] are not at the top, it’s a chance to get in.”

So how does this end? Is someone new really going to jump into the race? If so, will his or her campaign be viable? I tend to think that a last-ditch candidacy can’t win, unless maybe we are talking about someone really popular and well-known like Michelle Obama. I don’t think someone like Patrick has much of a chance to knock off Biden or Warren, who have been campaigning for months, raised millions of dollars and have staff on the ground in key states. I can’t rule out one of these people running anyway — Bloomberg and Patrick in particular have long flirted with running for president. They want the job, so maybe they convince themselves there is a path to get it even if there really isn’t.

But, in the end, I’d bet that the party establishment will accept whomever does well in primaries in February and March. I don’t think Bloomberg himself will ever endorse Warren if she does well in those first few contests, but he represents something of an extreme case. Would, for example, former top Obama aide Valerie Jarrett endorse the Massachusetts senator if she won the first four primaries, essentially signaling that the former president is fine with Warren as the nominee? I think that’s very possible. Like the Republican Party in the 2016 primary cycle it doesn’t appear that the Democratic establishment will collectively decide who the nominee should be before the voters weigh in. But the party will likely decide at some point to get behind Biden, Buttigieg, Warren or Sanders — and this autumn angst will seem like a distant memory.