If issued, the subpoena would be the first as part of the panel’s joint conflict-of-interest investigation with the Senate Finance Committee. It also comes on the heels of Biden’s landslide victory in the South Carolina primary on Saturday, and ahead of several Super Tuesday contests that could shape the trajectory of the race for the Democratic presidential nomination.

President Donald Trump was impeached in December for allegedly pressuring the Ukrainian government to investigate the Bidens over similar allegations that the Senate committees are probing. The Senate acquitted Trump last month on a mostly party-line vote.

In his letter, Johnson said Michigan Sen. Gary Peters, the committee’s top Democrat, had objected to the subpoena in separate correspondence. Democrats have said there is no evidence to buttress the allegations that Biden or his son did anything wrong related to Hunter’s role on the board of Burisma.

Peters said he was “concerned that the United States Senate and this committee could be used to further disinformation efforts by Russian or other actors.” He also demanded that the committee receive “defensive briefings” from the U.S. intelligence community about the information the panel receives as part of the probe.

Indeed, some Republican senators have expressed similar concerns — both privately and publicly.

Senate Judiciary Committee Chairman Lindsey Graham (R-S.C.) has said senators should “take very cautiously anything coming out of the Ukraine against anybody.”

And in December, Senate Intelligence Committee Chairman Richard Burr (R-N.C.) met privately with Johnson and Sen. Chuck Grassley (R-Iowa), the Finance Committee chairman, to express similar concerns about the Senate’s Biden investigation, saying it could aid Russia’s efforts to sow chaos in American politics.

In his letter, Johnson said the report about his meeting with Burr was “inaccurate” but said he could not discuss the substance of any discussions he had in a classified setting.

“Apparently, some here in Congress believe they are above the law when they publicize the fact of a meeting and purported details of conversations that took occurred in a classified setting,” Johnson wrote.

Johnson said Blue Star and one of its former consultants, Andrii Telizhenko, provided some documents to the committee, but added that Telizhenko was barred from turning over some of the information due to his non-disclosure agreement with Blue Star.

“Blocking the receipt of relevant records, and any committee member voting against this subpoena would be doing, only heightens the risks of ‘disinformation’ because the committee would not have access to all pertinent information,” Johnson wrote.

Telizhenko, who has made unsubstantiated allegations of coordination between the Democratic National Committee and the Ukrainian government in 2016, met with Trump’s personal lawyer Rudy Giuliani earlier this year to discuss “Ukrainian collusion” with Democrats during the election.

Johnson pledged to go “to great lengths” to verify the information the committee receives.

Natasha Bertrand contributed to this report.

