Kurt Volker Kurt VolkerGOP senators request details on Hunter Biden's travel for probe Yovanovitch retires from State Department: reports Live coverage: Senators enter second day of questions in impeachment trial MORE, the Trump administration's former special envoy to Ukraine, on Monday announced his resignation as leader of the McCain Institute for International Leadership amid the furor over his role in efforts to pressure Ukraine to investigate the Biden family.

In a statement, Volker said he felt "the recent media focus on my work as U.S. Special Representative for Ukraine Negotiations risks becoming a distraction from the accomplishments and continued growth of the Institute, and therefore I am stepping down as Executive Director."

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Volker spent the last seven years working for the institute, which is a Washington-based think tank that functions in coordination with Arizona State University.

Cindy McCain, the widow of the late Sen. John McCain John Sidney McCainCrenshaw looms large as Democrats look to flip Texas House seat Analysis: Biden victory, Democratic sweep would bring biggest boost to economy The Memo: Trump's strengths complicate election picture MORE (R-Ariz.), thanked Volker for his work at the institute and "his dedication to my husband and the entire McCain family." She said former National Counterterrorism Center Director Nick Rasmussen will take over as the acting executive director.

The New York Times reported last week that Volker was expected to step down as he emerged as a central figure in the Ukraine scandal that triggered a formal impeachment inquiry into President Trump Donald John TrumpFederal prosecutor speaks out, says Barr 'has brought shame' on Justice Dept. Former Pence aide: White House staffers discussed Trump refusing to leave office Progressive group buys domain name of Trump's No. 1 Supreme Court pick MORE.

Trump urged Ukrainian President Volodymyr Zelensky on a July 25 call to "look into" Democratic presidential candidate Joe Biden Joe BidenFormer Pence aide: White House staffers discussed Trump refusing to leave office Progressive group buys domain name of Trump's No. 1 Supreme Court pick Bloomberg rolls out M ad buy to boost Biden in Florida MORE and his son and to get in touch with his personal attorney Rudy Giuliani Rudy GiulianiThe Hill's Campaign Report: GOP set to ask SCOTUS to limit mail-in voting CIA found Putin 'probably directing' campaign against Biden: report Democrats fear Russia interference could spoil bid to retake Senate MORE and Attorney General William Barr Bill BarrFederal prosecutor speaks out, says Barr 'has brought shame' on Justice Dept. Why a backdoor to encrypted data is detrimental to cybersecurity and data integrity FBI official who worked with Mueller raised doubts about Russia investigation MORE on the matter.

Text messages released by House Democrats last week showed that Volker had indicated to one of Zelensky's aides that a visit to the White House was contingent on Ukraine carrying out the investigations Trump sought related to the Bidens and the 2016 election.

In a deposition with House lawmakers, Volker sought to distance himself from the efforts to investigate Biden. He defended the former vice president's character and blamed Giuliani for convincing Trump that the unsubstantiated corruption allegations against the Bidens were worth pursuing.