(The Hill) — Former President Barack Obama on Thursday said he still holds regrets for failing to see the rampant spread of disinformation within the U.S. while he was president, particularly around the 2016 election.

In a speech at Stanford University on the dangers of disinformation, Obama touched on the 2016 election, which U.S. intelligence has long confirmed Russia meddled in.

The former president said no one in his administration was surprised Russia had spread disinformation across social media platforms in an effort to sway the U.S. election, but he regretted not fully understanding how vulnerable America had become to such content.

“What does still nag at me though was my failure to fully appreciate at the time just how susceptible we had become to lies and conspiracy theories, despite having spent years being a target of disinformation myself,” Obama said, seeming to reference the racist and unfounded conspiracy theory that he was not born in the United States.

In the speech, Obama expressed his fears about disinformation in the digital age and the new information ecosystem, warning it was imperiling democracy.

He took a dig at Russian President Vladimir Putin and Steve Bannon, who served as a strategist for former President Donald Trump, for amplifying disinformation, saying people like them “understand it’s not necessary for people to believe this information in order to weaken democratic institutions.”

“You just have to flood a country’s public square with enough raw sewage. You just have to raise enough questions, spread enough dirt, plant enough conspiracy theorizing, that citizens no longer know what to believe,” Obama said.

In the lead-up to the 2016 election, Russian actors used social media platforms such as Facebook to spread false or misleading information online, among other efforts to interfere.

Obama also pointed out that disinformation was developing in other advanced and insidious ways, citing fake information in the COVID-19 pandemic and in the 2020 election, which Trump and his supporters falsely claim was stolen, as examples.

Obama said the seeds for the spread of disinformation existed before Russian meddling in the 2016 election.

“Putin didn’t do that. He didn’t have to,” Obama said. “We did it to ourselves.”