Mr. Warner has no such reticence.
“We have a president who remains unwilling to acknowledge the threat that Russia poses to our democracy,” Mr. Warner said. He said the use of automated messages, known as bots, and other social media tools were manipulated by Kremlin-linked actors to influence the election.
“The fact is that this Russian weapon has already proven its success and cost effectiveness,” Mr. Warner said.
Democrats and Republicans alike harshly criticized the companies for their slow response to the investigations. The greatest scrutiny was aimed at Facebook, whose general counsel, Colin Stretch, disclosed that 150 million users of both Facebook and its subsidiary Instagram were exposed to content spread by a Russian-linked company called the Internet Research Agency.
But Senator Marco Rubio, Republican of Florida, emphasized that the real intent of Russian propaganda was to broadly spread misinformation and create chaos.
“These operations, they’re not limited to 2016 and not limited to the presidential race, and they continue to this day. They are much more widespread than one election,” Mr. Rubio said.
The comments contrasted starkly with those of Democrats and made plain the political tensions that are shaping investigations into Russian meddling in the 2016 election.
Senator Martin Heinrich, Democrat of New Mexico, also took aim at Mr. Trump’s dismissal of the role of Russia-created social media in his win. Mr. Heinrich challenged Mr. Stretch to acknowledge such content and the role that fake accounts linked to Russia and other misinformation had in the election.
“Last month, President Trump called Russian purchased Facebook ads a ‘hoax.’ I’ve looked at those Russian-sponsored Facebook ads. I certainly hope you’ve had a chance to review them. Are they, in fact, a hoax?” Mr. Heinrich said.
Mr. Stretch said no. “The existence of those ads were on Facebook,” he said, “and it was not a hoax.”