The Senate confirmed Stephen Biegun as deputy secretary of state on Thursday, giving Mike Pompeo an official second-in-command amid speculation about him making a potential Senate bid in Kansas.

The Senate voted 90 to 3 to confirm Biegun, who has been serving as the Trump administration’s top negotiator with North Korea since mid-2018 and has been praised by Republicans and Democrats for his work in the role.

Before that, he worked for about 15 years as a foreign policy adviser on Capitol Hill, on the White House National Security Council under President George W. Bush, and in various roles in the private sector, including a stint in Russia.

Biegun will take on his supervisory role at the State Department as the Senate prepares for President Trump’s impeachment trial, in a case that hinges largely on the testimony of current and former State Department employees.

In his confirmation hearing last month, Biegun said he knew one of the star witnesses in the House’s impeachment inquiry, former U.S. ambassador to Ukraine Marie Yovanovitch, from years ago when both were posted in Moscow. He told lawmakers that it was “clear to me that an outside party based in Ukraine slandered her,” leading to her ouster in May.

He also promised that “there will not be disciplinary action by the State Department against any of our employees who are testifying under subpoena” in the impeachment inquiry, despite admonitions from the White House and State Department against participating.

Biegun’s new boss, Pompeo, has come under fire from lawmakers for not doing more to protect Yovanovitch from the efforts of Trump’s lawyer, Rudolph W. Giuliani, to push her aside. Ambassador William B. Taylor Jr., who stepped into the job at Pompeo’s request after Yovanovitch’s ouster, is leaving his post at the beginning of next month, just ahead of Pompeo’s first trip to Ukraine.

Pompeo has dismissed questions about whether he is considering a Senate bid.

In a tweet congratulating Biegun, Pompeo said, “I’m looking forward to working with you to ensure steadfast American leadership in the face of today’s biggest challenges.”

Senate Democrats seemed less concerned during Biegun’s confirmation hearing about how well he might work with Pompeo than they were with how Biegun might do filling his shoes.

“Given the expectation that Secretary Pompeo will leave the Department early next year to run for Senate . . . your nomination takes on even greater significance,” Sen. Robert Menendez (D-N.J.) told him.

In the meantime, Biegun as deputy secretary will be take on responsibility for personnel matters at a time when morale at the department is flagging.

Menendez also speculated that Biegun might have to step into Pompeo’s role when it comes to determining what documents Congress has a right to see pertaining to Trump’s activities vis-a-vis Ukraine, as some witnesses have testified that Pompeo was in the loop.