Murphy’s letter comes the same day that the Senate Homeland Security and Governmental Affairs Committee is set vote to subpoena documents from a former consultant for Blue Star, a Democratic public affairs firm, as part of a broader effort to look into Hunter Biden’s role advising Burisma while his father was vice president and working on Ukrainian affairs. The committee’s chair, Sen. Ron Johnson (R-Wis.), said last week he is likely to release an interim report about his probe into Hunter Biden’s relationship with Burisma within one to two months.

Johnson and Senate Finance Committee Chair Chuck Grassley (R-Iowa) have also requested the State Department release any documents related to Hunter Biden. In addition, they've asked the National Archives and Records Administration for records of any White House meetings in 2016 between Obama administration officials, representatives of the Ukrainian government and the Democratic National Committee officials, as part of an effort to investigate Ukraine's role in the 2016 election. There's no evidence of a top-down effort from the Ukrainian government to interfere U.S. politics.

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Murphy, in the interview, said it’s not coincidental that Senate Republicans are ramping up their probe following Biden’s surge in the Democratic primary.

“Our responsibility is to make sure that the official letters of the government aren't used to destroy people's political opponents — that seems to be a theme in this administration,” Murphy said. “I expect Democrats are going to have to spend time explaining why it's illegitimate for Senate Republicans to use their position to try to destroy the Bidens.”

In his letter, Murphy requests that the inspectors general explain whether their agency has cooperated with any congressional requests related to Hunter Biden or Burisma; the extent of their compliance; if the agency cooperated with other congressional requests, including probes Trump’s tax returns; and if there have been different standards applied for probes into Trump’s political opponents compared to probes into the president.

He requested a response by March 23.

