“We see much less of that kind of experimentation with the Democratic candidates,” said Laura Edelson, a researcher at New York University who tracks political advertising on Facebook. “They’re running fewer ads. We don’t see the wide array of targeting.”

The Trump campaign, she said, “is like a supercar racing a little Volkswagen Bug.”

The Democrats would be the Volkswagen. They are largely running what other experts and political operatives compared to brand-loyalty campaigns, trying to sway moderates and offend as few people as possible, despite mounting research that suggests persuasion ads have little to no impact on voters in a general election.

The candidates, to be sure, are collectively spending more on Facebook and Google than on television and are trying to target their ads — Mr. Biden’s tend to be seen by those born before 1975, for instance, while Senator Bernie Sanders’s are aimed at those born later. But without the same level of message testing and data collection, the Democrats’ efforts are not nearly as robust as Mr. Trump’s.

[Read more on how Democrats are using Facebook to reach specific voters.]

Democratic digital operatives say the problem is a party dominated by an aging professional political class that is too timid in the face of a fiercely partisan Republican machine. The Biden campaign’s decision to tack from digital to television, they say, is only the most glaring example of a party hung up on the kind of broad-based advertising that played well in the television age but fares poorly on social media.

The digital director of a prominent Democratic presidential campaign recounted how he was shut down by an older consultant when pressing for shorter, pithier ads that could drive clicks. “We don’t need any of your cinéma vérité clickbait,” the consultant snapped, according to the digital director, who spoke on the condition of anonymity to avoid risking his job.

Other digital consultants and campaign officials told similar stories, and complained that the Democratic establishment was too focused on winning over imagined moderates, instead of doing what the Trump campaign has done: firing up its base.

“It’s true that anodyne messaging doesn’t turn anyone off. But it doesn’t turn them on either,” said Elizabeth Spiers, who runs the Insurrection, a progressive digital strategy and polling firm.