Facebook decided on Friday to allow a type of paid political message that had sidestepped many of the social network’s rules governing political ads, in a reversal that highlights difficulties tech companies and regulators have in keeping up with the changing nature of paid political messages.

Facebook’s policy change comes days after the Democratic presidential candidate Mike Bloomberg exploited a loophole to run humorous messages promoting his campaign on the accounts of popular Instagram personalities followed by millions of younger people.

The Bloomberg campaign had paid more than a dozen social media influencers to post Bloomberg memes using their Instagram accounts, each of which has millions of followers.

The memes showed the 78-year-old candidate, in a tongue-in-cheek awkward fashion, chatting with popular social media influencers like “Tank Sinatra”, asking them to help him raise his profile among younger people.

“Can you post a meme that lets everyone know I’m the cool candidate?” Bloomberg wrote in one of the exchanges posted by an account called FuckJerry, which has nearly 15 million followers on Instagram. The candidate then sent a photo of him wearing baggy chino shorts, an orange polo and a zip-up vest.

The Bloomberg posts weren’t much more than self-deprecating humor used to sell the candidate’s old guy appeal, using a tactic that until now was largely used to sell skin-care products or clothing-subscription services.

But the lack of oversight and clear rules around influencer marketing, not to mention their effectiveness in reaching younger audiences, makes them ripe for misuse.

In fact, Bloomberg’s effort skirted many of the rules that tech companies have imposed on political ads to safeguard US elections from malicious foreign and domestic interference and misinformation.

Online political ads have been controversial, especially after it was revealed Russia used them in an attempt to influence the 2016 presidential election. In response, Facebook has rolled out a number of rules to prevent a repeat of that, though it has declined to factcheck political ads and refuses to ban even blatantly false messages.

“This is a new kind of activity that simply didn’t exist when the rules for internet political communications were last updated,” said Commissioner Ellen L Weintraub of the Federal Election Commission.

Friday’s policy change involves what Facebook calls “branded content”, sponsored items posted by ordinary users who are typically paid by companies or organizations. Advertisers pay the influential users directly to post about their brand.

Facebook doesn’t make money directly from such posts and doesn’t consider them advertising. As a result, branded content wasn’t governed by Facebook’s advertising policies, which require candidates and campaigns to verify their identity with a US ID or mailing address and disclose how much they spent running each ad.

Until Friday, Facebook tried to deter campaigns from using such branded content by barring them from using a tool designed to help advertisers run such posts on Facebook and Instagram, which is owned by Facebook.

The rule change now allows campaigns in the US to use this tool, provided they have been authorized by Facebook to run political ads and disclose who paid for the sponsored posts. Campaigns that avoid using the tool, as Bloomberg had, risk having their accounts suspended.

“After hearing from multiple campaigns, we agree that there’s a place for branded content in political discussion on our platforms,” Facebook said in an exclusive statement to the Associated Press. “We’re allowing US-based political candidates to work with creators to run this content.”

Politicians still will not be required to disclose how much they paid the influencers to run the posts. And the posts will not appear in Facebook’s ad library, which publicly catalogs political ads and allows other campaigns, journalists and watchdog groups to view the type of messages politicians are pushing in the election.

Facebook’s new rules will not apply to someone merely creating or sharing a post about a politician without getting paid.

The Bloomberg campaign declined to say how much it paid for the sponsored posts, or if it had more in the works.