Facebook’s chief operating officer, Sheryl Sandberg, and Twitter CEO Jack Dorsey are to testify before the Senate Select Committee on Intelligence, a generally bipartisan body whose members tend to refrain from trying to score cheap political points. Google CEO Sundar Pichai declined an invitation to attend the hearing.

Then later on Wednesday afternoon, Dorsey will testify before the House Commerce Committee, a much larger body that is rife with deep partisan disputes. There the focus will be on whether Twitter has discriminated against conservatives.

The Senate hearing is expected to delve into detail about prior foreign influence operations, particularly the Russian-linked attack on the 2016 presidential election. The tech companies have already offered substantial information about the extent of the Russian efforts and apologized for failing to block the attacks.

“We were too slow to spot this and too slow to act. That’s on us,” Sandberg plans to say, according to an early release of her testimony. Actions taken since “show our determination to do everything we can to stop this kind of interference from happening.”

Relying on both human content reviewers and artificial intelligence apps, Facebook says it disabled 1.27 billion fake accounts between October 2017 and March 2018 and took down 836 million pieces of spam in the first quarter of 2018 alone.

Sandberg and Dorsey are also expected to call on senators for more government assistance in combating the threats to the elections. “America has always confronted attacks from opponents who wish to undermine our democracy,” Sandberg is to say in her prepared remarks. “What is new are the tactics they use. That means it’s going to take everyone — including industry, governments, and experts from civil society — working together to stay ahead.”

The small group of senators on the Intelligence committee tend to be more serious and bipartisan in their approach than the dozens of House and Senate lawmakers who grilled Facebook CEO Mark Zuckerberg in April on all manner of subjects, from election interference to alleged biased against conservative views. But they’ll likely press the two executives for more details about the extent of foreign interference ahead of the 2018 elections and the countermeasures that the companies have created.

But don’t expect as much political grandstanding. Chairman Sen. Richard Burr (R-N.C.) and vice chairman Sen. Mark Warner (D-Va.) tend to work together more closely than the representatives on the more politically-split committees that heard from Zuckerberg. For example, even as House Republicans issued a report raising questions about whether Russia interfered with the 2016 election, Burr’s committee in July released its findings that Russian meddling was “extensive and sophisticated.”

Sen. Warner issued a report in July with 20 potential ways for major tech companies better fight foreign attacks, protect consumer privacy and promote competition. Although some of the ideas were recycled, run of the mill policy proscriptions, the paper also discussed making sites like Facebook (FB) and Google (GOOGL) liable for “defamation, invasion of privacy, false light, and public disclosure of private facts” and enacting a broad privacy law along the lines of Europe’s General Data Protection Regulation.

Warner said in an interview with Wired that he planned to ask about some of those matters, though with the major focus on election security, misinformation, and disinformation. “I don’t want this to be a retrospective on what happened in 2016, but I want to know what they’re doing to prevent this happening in 2018 and beyond,” Warner said.

Although it probably won’t come up in the senate, House Republicans no doubt will question Dorsey about a report in the Wall Street Journal this week that said he personally weighed in on decisions whether to suspend Twitter (TWTR) users like Alex Jones, the talk show host who spread conspiracy theories. Twitter has said its CEO did not influence the decisions, but the Journal’s report cited unnamed sources who said Dorsey changed the outcome of some inquiries at the last minute.

Dorsey plans to offer a strong denial that his company discriminates against any point view. “Let me be clear about one important and foundational fact: Twitter does not use political ideology to make any decisions, whether related to ranking content on our service or how we enforce our rules,” Dorsey said in prepared testimony for the House hearing. “We do not shadowban anyone based on political ideology. In fact, from a simple business perspective and to serve the public conversation, Twitter is incentivized to keep all voices on the platform.”