In an interview with The Hollywood Reporter in mid-January, Hillary Clinton said she considered Bernie Sanders unaccomplished and unlikable, with few friends on Capitol Hill. Then, last Friday, as though sensing the controversy generated by her remarks had faded all too quickly, Mrs. Clinton appeared on the liberal-minded podcast “Your Primary Playlist” to accuse Senator Sanders of failing to do enough to unite the party behind her candidacy after her primary win in 2016.

Mrs. Clinton was not alone in her apparently rising anxiety. Near the end of last month, the centrist think tank Third Way released a memo all but begging Iowans not to vote for Mr. Sanders. The former Democratic nominee John Kerry was reportedly overheard on Sunday contemplating several strategies to stop Mr. Sanders from taking the nomination. Meanwhile, Democratic National Committee members are considering shifts in convention rules tailored to hobble Mr. Sanders’s chances.

It is fair to conclude that the Democratic Party’s center is panicking, and it is now fair to conclude that it has good cause: With 62 percent of Iowa caucus results in, Mr. Sanders leads the popular vote, with 26.3 percent. He trails former Mayor Pete Buttigieg of South Bend, Ind., in state delegates by a slim margin. But with Mr. Buttigieg struggling in primary polls in New Hampshire and Nevada, it seems unlikely his campaign has the kind of momentum that could lead to the nomination. Thus, the greater Iowa upset is that heir apparent Vice President Joe Biden is a distant fourth. With Mr. Biden’s front-runner status compromised, Mr. Sanders emerges from Iowa as a formidable candidate — without establishment imprimatur.

Mr. Sanders leads the popular vote in Iowa not because he is favored by entrenched powers within the Democratic Party or because he has institutional support in the form of steady contributions from policy-minting think tanks, big donors or major political pundits.