(CNN) A Senate committee voted along party lines Wednesday to issue a subpoena as part of the Republican-led investigation into the Ukrainian energy firm that hired former Vice President Joe Biden's son, Hunter Biden.
The subpoena is one of several steps Senate Republicans are taking to ramp up probes related to the Obama administration and Biden, the presumptive Democratic presidential nominee who will likely challenge President Donald Trump in the 2020 election.
The Senate Homeland Security and Governmental Affairs Committee voted 8-6 to authorize the subpoena Chairman Ron Johnson requested for Blue Star Strategies, a US public affairs firm that worked with Burisma, the Ukrainian company which hired Biden. Democrats denounced the investigation as a partisan effort to help Trump's reelection bid.
It's the first subpoena authorized in Johnson's investigation into Burisma and Hunter Biden that ramped up following the end of the impeachment trial. The Wisconsin Republican has received documents from the State Department and National Archives and says he expects to release a report laying out the committee's findings in the coming months.
Before the pandemic, Trump suggested he would make Ukraine a major part of a campaign against Biden, while Trump and his allies have repeatedly made unfounded and false claims alleging that Biden and his son acted corruptly in Ukraine. Burisma was a focus of last year's impeachment proceedings, as it was the company Trump asked Ukrainian President Volodymyr Zelensky to investigate in their July 2019 call.
One of the Republicans who voted for the subpoena Wednesday, Sen. Mitt Romney of Utah, still has reservations about the probe itself. Asked if he thought the investigation was political, Romney told CNN: "Yeah, I do."
In addition to Johnson's probe, Senate Judiciary Chairman Lindsey Graham is investigating the origins of the FBI's investigation into Russian meddling in the 2016 election and the foreign surveillance warrants obtained for a former Trump adviser, Carter Page. Graham, a Republican from South Carolina, is planning to hold a vote next month giving him broad subpoena power on matters related to the Russia probe -- and says he's eying a report in September or October, before the election.
Johnson, Graham and GOP Sen. Chuck Grassley of Iowa have all requested that acting Director of National Intelligence Richard Grenell provide declassified documents to Congress, including related to the FBI's investigations and "unmasking" requests made during the end of the Obama administration.
Grenell, a close Trump ally, has rapidly complied with the requests, providing the Republicans with declassified documents that they have released -- and Trump has used as a cudgel to attack Biden and accuse former President Barack Obama of committing an unspecified crime. Trump on Tuesday told Republicans at a closed-door lunch on Capitol Hill that they should get "tough" on "unmasking," which is the process of certain US officials requesting to view the names of Americans in foreign intelligence reports who are hidden, or "masked," according to two sources.
The Senate Republican probes were endorsed Tuesday by Senate Majority Leader Mitch McConnell, who made a speech on the Senate floor defending the President's attacks on the Russia investigation, a sign of the Senate GOP and Trump aligning on the matter heading into the election.
"So, look: No matter what some Washington Democrats may try to claim, you are not crazy or a conspiracy theorist if you see a pattern of institutional unfairness towards this President," McConnell said. "You would have to be blind not to see one."
On Tuesday, Graham requested additional documents related to "unmasking" during the Trump transition. Then Johnson and Grassley asked Grenell to provide unmasking requests throughout January 2016 that included members of the Trump campaign.
The unmasking requests released last week were the result of authorized individuals following standard National Security Agency procedures for unmasking intelligence reports that included a legitimate justification for the unmasking, the NSA said in its declassification memo. The officials making the requests do not know who they are seeking to unmask because the name is hidden. Unmasking requests are routinely made as part of normal intelligence work in both the Obama and Trump administrations, and the numbers have been higher in recent years.
Wednesday's meeting to approve the subpoena was an unusually heated affair for the Homeland Security Committee. Democrats angrily denounced the probe that Johnson was conducting, arguing the committee should be focused on investigating the coronavirus pandemic. When Johnson tried to call the vote after several Democrats had spoken, saying others could speak afterward, Democratic Sen. Tom Carper of Delaware demanded five minutes before the panel held a roll call vote.
"At this moment, when Americans need us to work together, this extremely partisan investigation is pulling us apart," said Sen. Gary Peters of Michigan, the top Democrat on the Committee. "This is not a serious bipartisan investigation in the tradition of this committee and I believe we should not be going down this dangerous road."
Johnson argued that the committee has conducted "all kinds of oversight" related to coronavirus and was able to both examine the response to the pandemic and conduct the Burisma investigation.
"That has been by far, what most of us have spent our time on is addressing this horrific crisis that faces this nation," Johnson said. "It was not my desire to even publicize this ... I just want the American people to understand the truth."
Johnson said that the subpoena his committee approved Wednesday included requests for documents and depositions with the top two officials at Blue Star Strategies.
Biden campaign spokesman Andrew Bates accused Johnson of "running a political errand" for Trump with the subpoena.
Blue Star Strategies did not respond to CNN's requests for comment. But Blue Star's CEO, Karen Tramontano, wrote a letter to the committee on Wednesday saying the firm had provided answers to the committee in December 2019 and twice this week when additional information was requested.
"At every opportunity we have indicated to the committee that it is our intention to cooperate," Tramontano wrote. "At no time have we ever stated or indicated in any way that we would not cooperate. Therefore, we are puzzled, despite our willingness to cooperate, why the committee is proceeding to vote on a subpoena."
Johnson said at Wednesday's meeting he refuted Blue Star's letter, but he did not elaborate.
Austin Altenburg, a spokesman for Johnson, said in a statement that Blue Star "has delayed our efforts for more than five months" and did not allow committee staff to speak to the firm's attorney until last week.
"Their only real efforts came after we noticed this markup, and we know even those have been woefully incomplete," Altenburg said. "We are looking forward to receiving a full response to all of our questions."
This story has been updated with additional developments Wednesday.