“Facebook cannot be trusted to regulate itself,” tweeted Rhode Island Representative David Cicilline on Wednesday night.

Mr. Cicilline, who is likely to chair the House of Representative’s Judiciary subcommittee that focuses on antitrust law, was responding to a Times investigation, one that painted a damning picture of how Facebook had handled the discovery of Russian misinformation campaigns on its platform. Based on interviews with more than 50 people, the investigation depicted Facebook’s top executives — including Sheryl Sandberg and Mark Zuckerberg — ignoring and downplaying the extent of Russian skulduggery, even going as far as to stall the publication of internal findings.

On Thursday, Facebook pushed back in a blog post that denied slow-rolling its response to foreign election interference.

But familiar questions remain unanswered: How much did Facebook know, and when?

The answers to those questions grow in size and seriousness as the breadth of the effort to befoul the democratic process becomes more and more apparent. In February, the special counsel Robert Mueller brought an indictment against an infamous Russian troll farm, the Internet Research Agency. In July, Mr. Mueller secured an indictment against 12 Russian intelligence officers for their roles in the hacking of the Democratic National Committee’s computers and those of Hillary Clinton’s presidential campaign. The same officers used both Facebook and Twitter to promote the stolen documents and emails.