(CNN)The top Democrat on the Senate Judiciary Committee is accusing the panel's Republican chairman of not wanting to dig deeply into the Russia investigation, the latest sign of rising partisan tensions on Capitol Hill over President Donald Trump and Russia.
Senate Judiciary chairman, top Democrat clash over Russia investigation
Sen. Dianne Feinstein of California has sent a slew of letters in recent weeks seeking documents and interviews from a host of key witnesses in the Trump orbit — and Senate Judiciary Chairman Chuck Grassley's has not signed on.
"We want him to sign on. I think there's an effort -- subtle -- not to go deeply," Feinstein said. "I hadn't realized it before. But I realize it now. And we're going to have to find a way to deal with it."
Grassley told CNN Tuesday that he's not stalling the committee's probe as Feinstein suggested, saying they were working to come to consensus on a range of issues.
"When she wants to send letters, she sends them to us, and if we want to sign on, we do that ... And she can decide to sign on the letters that we have," Grassley said. "And then the bottom line of it is that if people come up here as a result of her letters or my letters to be questioned, then her staff and my staff can sit in on each other's and ask questions. So at the level of actually asking questions, there's a great deal of cooperation."
And Grassley spokesman Taylor Foy said that Feinstein herself was not signing onto letters that Grassley had sent seeking information about the FBI's handling of the investigation into former Democratic presidential candidate Hillary Clinton's private server during the 2016 election, including an effort to interview FBI agent Peter Strzok, who was removed from special counsel Robert Mueller's investigation after sending messages that appeared to mock Trump.
"Chairman Grassley's inquiry is looking at decisions made by Justice Department and the FBI during politically charged investigations spanning two administrations," Foy said. "We now know that an FBI official involved in both the Clinton email investigation and the Russian interference probe had expressed pro-Clinton and anti-Trump views. This is exactly the type of improper political influence that the Judiciary Committee should be concerned about."
Feinstein's criticism of Grassley comes after she argued this weekend following the guilty plea of former national security adviser Michael Flynn that a case was building against Trump for obstruction of justice.
"I think what we're beginning to see is the putting together of a case of obstruction of justice," Feinstein said Sunday on NBC's "Meet the Press." "I think we see this in the indictments, the four indictments and pleas that have just taken place, and some of the comments that are being made. I see it in the hyper-frenetic attitude of the White House: the comments every day, the continual tweets. And I see it, most importantly, in what happened with the firing of (FBI) Director (James) Comey, and it is my belief that that is directly because he did not agree to lift the cloud of the Russia investigation. That's obstruction of justice."
Other Democrats on the Senate Judiciary Committee have also expressed frustration with Grassley over how quickly the committee's Russia probe is moving. The panel is one of three committees on Capitol Hill with active investigations into election meddling and possible collusion.
"I continue to be disappointed about the pace of the investigation, and now the Flynn guilty plea should give real urgency to the obstruction of justice investigation," said Sen. Richard Blumenthal, a Connecticut Democrat.
Distrust between Democrats and Republicans is also bubbling on the House Intelligence Committee, where Democrats have criticized the role played by Chairman Devin Nunes, the California Republican who stepped aside from leading the Russia probe but has continued to be involved in signing off on committee subpoenas.
Nunes is currently threatening to hold top officials at the Justice Department and FBI with contempt of Congress if they do not meet his subpoena demands over documents related to the Trump opposition research dossier.
And the Senate Intelligence Committee's top Democrat, Mark Warner of Virginia, is calling for Trump son-in-law and White House adviser Jared Kushner to return to the committee and testify again, after his role in directing Flynn to reach out to Russian ambassador Sergey Kislyak was disclosed in Flynn's guilty plea.
Senate Intelligence Chairman Richard Burr would not say Monday whether he agreed with Warner about Kushner returning.
"You need to talk to Mark then," Burr said when asked about Warner's Kushner comments. "If I think he needs to come back, I'll invite him back."
This story has been updated and will continue to update with more developments.