Senate Judiciary Committee Chairman Lindsey Graham is scheduling a vote that would allow him to subpoena more than 50 current and former officials who were involved in the Justice Department's investigation of Russian involvement in the 2016 U.S. presidential campaign, as Donald Trump and his allies have launched a broad election-year attack on the investigation as a "deep state" conspiracy.

Graham, a close ally of Trump, is effectively turning the investigation on the investigators, asking the officials for documents, communications, and testimony about the FBI's investigation into ties between Russia and the 2016 Trump campaign.

Republicans in Congress have already been probing the probe for several years, and many of the officials have already sat for extensive testimony about their roles. The Justice Department has also investigated the investigation, and an internal report released last year documented a series of problems with it.

The newest probe, though, could be the most extensive so far. Trump has focused on Barack Obama, but Graham has made clear that he won't call in the former president. Still, Graham said last week he wanted to know "why and how the system got so off the rails," and he announced Monday that the panel will hold a vote in early June to authorize it to compel information from those involved.

Among the officials on the list are former FBI Director James Comey, former FBI Deputy Director Andrew McCabe, former Director of National Intelligence James Clapper, and former CIA Director John Brennan. The list also includes some current officials who have dealt with the probe, including Attorney General William Barr and FBI Director Christopher Wray. The June vote would not be to subpoena the officials but to authorize Graham to do so.

The vote is a rare move for the panel, which has traditionally issued bipartisan subpoenas. Aware that the top Democrat, California Sen. Dianne Feinstein, would oppose the move, Graham said he would hold a vote instead. Acknowledging that the committee doesn't normally send partisan subpoenas, a statement from Graham's office points to a 2008 partisan committee vote as precedent.

The Russia investigation began within the FBI during the 2016 election and was taken over by special counsel Robert Mueller a year later. After a two-year investigation, Mueller issued a report in April 2019 that identified substantial contacts between Trump associates and Russia but did not allege a criminal conspiracy between his campaign and the Kremlin. Mueller also examined about a dozen possible instances of obstruction of justice and said he could not exonerate Trump on that point.

Now, Trump and his allies are working reframe the entire investigation. In recent weeks, the Justice Department has decided to end its prosecution of former Trump administration national security adviser Michael Flynn, who pleaded guilty to lying about a conversation with the Russian ambassador. Republicans on Capitol Hill released a list of Obama administration officials who they say may have learned Flynn's identity from intelligence reports in 2016 and 2017. Among the names is Trump's Democratic opponent, Joe Biden, who was vice president when the Russia probe began.

Such requests are common, including during the Trump administration, which has made thousands of "unmasking" requests.

Graham has said the committee also will look into potential abuses of the Foreign Intelligence Surveillance Act, or FISA, during a probe of former Trump campaign adviser Carter Page. The FBI identified Page during the early days of its investigation and secretly targeted his electronic communications.

The inspector general's report released last year concluded that the FBI made significant errors and omissions in applications it made to the FISA court for the authorization to eavesdrop on Page. Those mistakes prompted internal changes within the FBI and spurred a congressional debate over whether the bureau's surveillance tools should be reined in.