New York (CNN) A few years ago, then President Barack Obama was appearing at dinner and on stage with Facebook CEO Mark Zuckerberg, and Nancy Pelosi was heaping praise on COO Sheryl Sandberg for "inspiring women across the world to believe in themselves."

Now, top Democrats appear to be going to war withand its leadership.

On Thursday, Pelosi ripped Facebook , calling it a "shameful" company. She accuseditof being "accomplices for misleading the American people with money from god-knows where."

He also called for revoking a major law protecting Facebook from being liable for what is posted on its platform.

Facebook has so far been silent in response to the renewed criticisms. The company declined to comment on Pelosi's remarks Thursday and did not immediately respond to a request for comment on Biden.

Where did it all go wrong?

Tensions first appeared to boil over after the 2016 election when, according to Special Counsel Robert Mueller, Russians used Facebook as part of a campaign to undermine the candidacy of former Secretary of State Hillary Clinton.

Since then, Facebook has also faced mounting scrutiny on both sides of the political aisle — but especially from Democrats — over what is seen by lawmakers as its market dominance as well as the perception, expressed in an interview published this week with Democratic presidential nominee Pete Buttigieg, that Zuckerberg has too much power.

Facebook's refusal to remove a doctored video of Pelosi last May clearly irked Democrats, including Clinton, who called the video "sexist trash" and suggested the argument for taking it down "wasn't even a close call."

But what really hit a nerve with Democrats more recently was Facebook's insistence last September that it would not fact-check ads from politicians — a policy many Democrats saw as beneficial to Trump's reelection campaign.

Facebook, the Democratic National Committee said, was allowing Trump "to mislead the American people on their platform unimpeded."

Sen. Elizabeth Warren ran a deliberately false ad to highlight what Democrats saw as the ludicrousness of the policy. The false ad claimed Zuckerberg had endorsed Trump's reelection campaign.

When Biden's campaign demanded Facebook remove a false ad from the Trump campaign accusing Biden of corruption of his role in Ukraine policy during the Obama administration, Facebook refused.

"Our approach is grounded in Facebook's fundamental belief in free expression, respect for the democratic process, and the belief that, in mature democracies with a free press, political speech is already arguably the most scrutinized speech there is," Katie Harbath, Facebook's head of global elections policy wrote in response last October.

But Facebook often appears to be the Democrats' favored target — even as leading Democratic candidates for president continue to sink money into the platform for their campaigns.

As with so much about Facebook, it's complicated.