These are the senators to watch in Tuesday's blockbuster hearing with Mark Zuckerberg

  • Facebook founder and CEO Mark Zuckerberg will testify at a joint hearing with the Senate's Judiciary and Commerce committees on Tuesday.

  • There are several senators to keep an eye on, as their history with Facebook and tech giants could produce tense back and forths.

WASHINGTON — All eyes will be on the Senate this Tuesday as Facebook founder and CEO Mark Zuckerberg testifies at a rare joint hearing with the upper chamber's Judiciary and Commerce committees.

The hearing, which will focus on privacy concerns, will allow senators to probe the social media mogul in ways he has never been publicly scrutinized before.

The Democrats

There are several key lawmakers to look for in the hearing.

  • Sen. Kamala Harris of California: She's a Democrat who has typically been an ally to Silicon Valley, a major piece of her constituency. At the same time, Harris, also a member of the Senate Intelligence Committee, has been vocal in going after bad actors in the investigation into attempts by the Russian government to interfere in the 2016 elections.

  • Sen. Amy Klobuchar of Minnesota: As Business Insider previously reported, Klobuchar was one of the first members of the Judiciary Committee to demand Zuckerberg come to Capitol Hill. In addition, Klobuchar, who also sits on the Commerce Committee, is a sponsor of the Honest Ads Act, which would bring online political ads into the same regulated sphere as the rest of campaign activities. Zuckerberg may have publicly backed the legislation last week, but it can still be expected to come up in the hearing.

  • Sen. Ed Markey of Massachusetts: He's been a longtime critic of large tech companies and Facebook in particular. Markey already sent a letter to Zuckerberg requesting information regarding the Cambridge Analytica scandal in advance of the hearing. Markey can be expected to take the gloves off when it is his turn to question Zuckerberg.

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The Republicans

Among Republicans, there are several to watch closely for potential fireworks in the hearing.

  • Sen. John Kennedy of Louisiana: A member of the Judiciary Committee, Kennedy wanted to bring Zuckerberg in several weeks ago. Kennedy, know on Capitol Hill for his folksy barbs and quick wit, has thrown curveball questions in hearings before, including relentlessly grilling one Trump administration nominee last year.

  • Sen. Ted Cruz of Texas: Also a member of the Judiciary Committee, Cruz has been a vocal critic of tech companies over what many conservatives believe are attempts to "censor" users on the right. When Facebook, Twitter, and YouTube sent officials to Capitol Hill in January, Cruz probed them over concerns among the far right that conservatives are treated unfairly through company policies and algorithms. Cruz went as far as to ask each company representative whether they engage in "shadow banning" conservative users, a theory that social media platforms deliberately suppress content produced from right-leaning users.

  • Sen. Lindsey Graham of South Carolina: For questions to be peppered at Zuckerberg from a national security angle on Tuesday, look no further than Graham, a member of the Judiciary Committee. Graham has previously gone after major tech companies. Graham probed representatives from Facebook, Twitter, and Google in a hearing last October about foreign actors that are of paramount concern, including Russia. Graham also suggested that legislative action might need to be taken to prevent abuses in the future.

The hearing is slated to last a few hours, beginning at 2:15 ET on Tuesday. Zuckerberg's will be one of the most high profile testimonies in months. On Wednesday, he will be back on Capitol Hill early in the morning to face the House Commerce Committee.

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