As he testifies before nearly half the U.S. Senate, Facebook CEO Mark Zuckerberg has his company's in-house legal and lobbying teams at his back.

Seated directly behind him today is Facebook Inc.'s vice president of U.S. public policy, Joel Kaplan, who served as President George W. Bush's deputy chief of staff from 2006 until the end of his administration. Also joining Zuckerberg were Facebook general counsel Colin Stretch; associate general counsel for compliance Pearl Del Rosario; chief privacy officer Erin Egan; and Myriah Jordan, a policy manager on congressional relations who was previously U.S. Sen. Richard Burr's general counsel. Brian Rice, director of public policy at Facebook, was also seated near Zuckerberg.

One adviser who wasn't in the hearing room was the outside lawyer who reportedly led Zuckerberg's hearing prep: Wilmer Cutler Pickering Hale and Dorr partner Reginald Brown, a veteran congressional investigations lawyer in Washington. He declined to comment Tuesday.

Facebook hired Kaplan in 2011 from the Texas utility giant Energy Future Holdings, where he had been an executive vice president handling the company's public policy and external affairs. After hiring Kaplan, Facebook said it was “imperative that we scale our policy team so that we have the resources in place to demonstrate to policy makers that we are industry leaders in privacy, data security and safety.”

Later that year, the social media giant hired Jordan, who had served with Kaplan in the Bush White House before becoming Burr's top lawyer, and lured Egan away from her partnership at Covington & Burling, where she led the global privacy and data security practice group.

Zuckerberg's appearance before Congress, his first since launching Facebook in 2004 from a Harvard dorm room, was prompted by the revelation that a political consultancy tied to the Trump campaign mined the data of an estimated 87 million users of the site to psychologically profile voters.

The scandal now engulfing Facebook has tested the company's lobbying team, which was already grappling with Congress' appetite to fight fake news and bring more disclosure to political advertising on social media following Russia's interference in the 2016 election.

For Facebook and its outside advisers at Wilmer, the two-day stretch of hearings presented the challenge of preparing a cerebral CEO to charm—or at least temper—lawmakers hungry to make a spectacle of a scandal that has touched millions.

Forsaking his signature t-shirt and hoodie, Zuckerberg donned a dark navy suit and blue tie for Tuesday's hearing and sat stoically as the chairman and ranking members of the Senate's Judiciary Committee hearings made their opening remarks, with Sen. John Thune saying that Facebook represents the American dream but adding that the company had an obligation to not create a “privacy nightmare.”

Zuckerberg is scheduled to testify Wednesday before the U.S. House Energy and Commerce Committee.

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