(CNN) Senate Homeland Security and Governmental Affairs Chairman Ron Johnson scrapped a planned vote Wednesday for a subpoena in the committee's Republican-led investigation into the Ukrainian energy firm that hired former Vice President Joe Biden's son.

The decision to postpone the subpoena vote came amid accusations from Democrats that the probe was politically motivated to damage Biden's presidential bid, as well as questions about the target of the subpoena, Andrii Telizhenko, an ally of the President's personal attorney, Rudy Giuliani. Telizhenko was a contractor for Blue Star Strategies, a public affairs firm that worked with Burisma, the Ukrainian energy company that hired Hunter Biden in 2013.

Johnson wrote a letter to committee members saying he was postponing the subpoena vote in order to allow time for senators to receive additional briefings -- and said he would now seek the records directly from Blue Star Strategies instead of Telizhenko. A committee source said that Johnson believes issuing a subpoena to Blue Star directly instead of Telizhenko, who had made unfounded allegations related to Ukrainian election meddling in 2016, was a "bipartisan path forward."

"Out of an abundance of caution, and to allow time for you to receive additional briefings, I will postpone a vote to subpoena records and an appearance from former Blue Star Strategies consultant Andrii Telizhenko about his work for the lobbying firm," Johnson wrote. "While we work through those questions, at the suggestion of both Republican and Democrat Committee members, we will instead go straight to the source and compel the same records and an appearance directly from Blue Star Strategies."

While Johnson, a Wisconsin Republican, has said that his investigation is unrelated to Trump's reelection bid, presidential politics have swirled over Johnson's probe and into Burisma and Hunter Biden. The investigation has been criticized by one Republican on the panel for being political, and Johnson himself charged earlier this month that the information he was seeking would be of interest to Democratic primary voters.

Johnson's investigation is one of several Senate Republican probes related to Ukraine that have ramped up in recent months as the presidential campaign season has gotten underway and Biden surged to become the frontrunner for the Democratic nomination.

Trump has also said that should Biden become the Democratic nominee, the Trump campaign would make Burisma and Ukraine a major campaign issue. Trump and his allies have repeatedly made unfounded and false claims to allege that the former vice president and his son acted corruptly in Ukraine.

A Democratic aide said Johnson has not notified Sen. Gary Peters, the top Democrat on the committee, of his intention to subpoena Blue Star Strategies. Peters can oppose the subpoena, which he did for Telizhenko, which then would require the chairman to put the matter to a full committee vote to issue the subpoena.

Johnson's move to change course on the subpoena is a signal of the uneasiness surrounding the investigation as the 2020 general election matchup looks to be taking shape between Trump and Biden.

When Johnson initially said the committee would vote on the subpoena last week, Sen. Mitt Romney expressed reservations about the investigation. But Johnson spoke with Romney and other members to ensure they were on board, the Utah Republican said Friday he would back the subpoena.

"I spoke with him about his commitment to only talk with the individual in a private setting as opposed to a hearing, and I felt that I was therefore going to protect that information," Romney said of Johnson.

Still, Romney isn't happy the committee is pursuing the investigation.

"I still believe that it's just as I said, I think it looks bad," Romney told CNN this week. "I think political investigations look bad, and I wish we weren't doing it."

Romney said he didn't know yet whether he would support future subpoenas in the probe, explaining that he wanted to see "where this investigation is going and what the intent is."

Johnson and Sen. Gary Peters of Michigan, the top Democrat on the Senate panel, traded accusations through letters in the leadup to Wednesday's vote. Peters, who opposed the subpoena when Johnson sought to issue it last month, which is what prompted the full committee vote, warned that the committee needed additional consultation with law enforcement and the intelligence community to ensure they weren't being used to promote Russian propaganda.

"This is a matter of national security, and our committee members must have the opportunity to get classified updates from our law enforcement and intelligence community to experts to prevent the committee from being used to advance information that could benefit foreign adversaries and undermine the integrity of our elections," Peters wrote in a letter to Johnson last week.

Johnson responded that he would not allow Russia to be used as a "smokescreen."

"As committed as I am to being on guard against the threat posed by our adversaries, I am equally dedicated to not letting foreign actors' malign actions and intentions be used as a smokescreen to inhibit or interfere with the Committee's legitimate and important oversight work," Johnson wrote.

Biden campaign spokesman Andrew Bates accused Johnson of "diverting the attention and taxpayer-funded resources of the Senate Homeland Security Committee away from the coronavirus outbreak, which was just designated a global pandemic, to clutch at a conspiracy theory that every fact-checker has debunked."

"In fact, Senator Johnson himself, joined by other Republicans, endorsed Joe Biden's work to get this corrupt prosecutor fired and signed a letter supporting that effort in 2015," Bates said in a statement.

Questions about Telizhenko's Ukraine allegations

Johnson said earlier this week that Telizhenko wanted to cooperate with the committee, but he could not because of a non-disclosure agreement. Now, Johnson is trying to get the records from Blue Star instead of Telizhenko himself. Blue Star Strategies did not respond to requests for comment.

"Listen, I didn't pick Telizhenko, Blue Star did," Johnson told CNN On Monday. "This is about records during his time of employment with Blue Star — very narrow. I don't see why anybody would be concerned about this."

Telizhenko charged that the criticisms of him were part of a smear campaign.

"There is a lot of pressure to shut me down and to discredit me," Telizhenko told CNN on Wednesday. "How can anyone say if my information is credible or not without seeing it or investigating it? It is all part of a smear campaign against anybody who comes out with the truth against the Democratic Party."

But Telizhenko's allegations about Ukraine have come under intense scrutiny.

Telizhenko is a stalwart Giuliani ally who has traveled with the former mayor and has promoted the conspiracy theory that Ukraine meddled in the 2016 election to weaken Democratic nominee Hillary Clinton and defeat Trump. That theory flies in the face of the unanimous assessment from US intelligence agencies that it was the Russian government who interfered in the 2016 election, and their goal was to elect Trump.

many When pressed for evidence in his interviews , Telizhenko often says he witnessed Ukrainian government's activities against Trump while working as a junior diplomat at the Ukrainian embassy in Washington. His LinkedIn profile says he worked as a "political officer" for seven months, ending in June 2016.

"He portrays himself to Ukrainians as having access in Washington, and I believe in Washington as being a conduit to certain Ukrainians," David Holmes, a senior US diplomat in Kiev, testified last year in a closed-door impeachment deposition. "What he actually does, I'm not sure."

Telizhenko's allegations first emerged in a January 2017 Politico article . He is quoted saying that he was instructed to work with a Democratic operative to dig into Paul Manafort, the onetime Trump campaign chairman who previously made millions working for corrupt Ukrainian politicians. (Manafort is currently serving a 7.5-year prison term for financial fraud relating to his Ukraine work.)

The article was frequently cited by Republicans during the impeachment proceedings to argue that Ukraine meddled in the 2016 election. The White House and many GOP lawmakers said it proved that Trump he was right to press for investigations into potential Ukrainian election meddling.

But senior Ukrainian officials disputed Telizhenko's account. The Ukrainian ambassador to the US at the time, Valeriy Chaly, told the Kyiv Post that Telizhenko was lying. Fiona Hill, who was the top White House adviser on Russia and later became a marquee impeachment witness, said the Politico article that quoted Telizhenko was cherry-picked and out of step with US intelligence.

"It does not amount to a large-scale Ukrainian government effort to subvert our elections which is comparable to anything that the Russians did in 2016," Hill said in her private deposition during the impeachment inquiry, referring to the allegations contained in the Politico article that Giuliani and others have championed.

Lt. Col. Alexander Vindman, who was a top White House adviser on Ukraine and had regular contacts with the Ukrainian embassy, testified in the impeachment inquiry that Telizhenko is "not a credible individual." Holmes, the US diplomat, also cast doubt on Telizhenko, telling lawmakers, "I don't think we found his perspective to be always credible and useful."

Despite the condemnation, Telizhenko became a fixture in right-wing media. He spread his allegations on Trump-friendly conspiracy sites like Infowars and Gateway Pundit, appeared on One America News Network, and gave an interview to The Hill's ex-columnist John Solomon, who coordinated his work with Giuliani and other Trump allies.

Some of that coverage highlighted his partnership with Giuliani, who has also championed many of the same conspiracy theories about Ukrainian election meddling. Last year, Telizhenko participated in meetings between Giuliani and two disgraced Ukrainian prosecutors who accused the Bidens of corruption, promoting claims that were largely debunked and discredited.

After those meetings, Giuliani returned to the US and urged the Justice Department and congressional Republicans to listen to the allegations and investigate the Bidens.

The media blitz continued even after impeachment wrapped up. Giuliani brought Telizhenko onto his podcast to discuss "evidence of Democrat bribery, extortion," and other alleged crimes. Telizhenko, speaking in English, repeated many of the same claims that he's made over the past few years, which have been largely debunked.

Telizhenko went on a retweet spree last week, sharing posts about the Senate subpoena and touting Trump's comment that he'll make Hunter Biden a "major" issue in the 2020 campaign.

This story has been updated with additional developments and an additional statement from the Biden campaign.