Sen. Chris Murphy Christopher (Chris) Scott MurphyDemocratic senator calls for 'more flexible' medical supply chain to counter pandemics The Hill's 12:30 Report - Presented by Facebook - Don't expect a government check anytime soon GOP chairman to release interim report on Biden probe 'in about a week' MORE (D-Conn.) said Sunday that special counsel Robert Mueller Robert (Bob) MuellerCNN's Toobin warns McCabe is in 'perilous condition' with emboldened Trump CNN anchor rips Trump over Stone while evoking Clinton-Lynch tarmac meeting The Hill's 12:30 Report: New Hampshire fallout MORE's investigation into alleged collusion between the Trump campaign and Russia has moved into a "new phase" after new documents were released to the public.

Murphy suggested the new phase is headed toward impeachment, comparing President Trump Donald John TrumpOmar fires back at Trump over rally remarks: 'This is my country' Pelosi: Trump hurrying to fill SCOTUS seat so he can repeal ObamaCare Trump mocks Biden appearance, mask use ahead of first debate MORE to former Presidents Clinton and Nixon.

"We have reached a new level in the investigation. The special counsel is starting to show his cards and these are very serious allegations," Murphy told ABC's "This Week."

"This is a president who's now named as an unindicted co-conspirator," Murphy said, referring to a filing in the case of Trump's former personal attorney Michael Cohen that implicates Trump in directing Cohen on illegal campaign contributions. "The allegation is that he committed at least two felonies to try to manipulate the 2016 election."

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Murphy added that it is important that Congress has "all of the facts."

"I think you are beyond the stage that led to impeachment proceedings against President Clinton," Murphy said. "I still think it's important for Congress to get all of the underlying facts and data and evidence that the special counsel has before we make that determination."

Murphy said that's why Congress needs Mueller's report "as soon as possible."

Sen. Chris Murphy: "I'm not going to give the House advice on whether or not to proceed with impeachment ... We have reached a new level in the investigation. The special counsel is starting to show his cards and these are very serious allegations" https://t.co/QasWMG5Ixy pic.twitter.com/ScapBzrhv6 — This Week (@ThisWeekABC) December 9, 2018

"We certainly have moved into a new phase," Murphy added. "The president has now stepped into the same territory that ultimately led President Nixon to resign the office. President Nixon was an unindicted co-conspirator."

"Certainly a different set of facts, but this investigation is now starting to put the president in serious legal crosshairs," he added.

On Friday, Mueller released a heavily redacted filing that detailed the special counsel's claim that former Trump campaign chairman Paul Manafort Paul John ManafortOur Constitution is under attack by Attorney General William Barr Bannon trial date set in alleged border wall scam Conspicuous by their absence from the Republican Convention MORE violated his plea agreement by lying to federal prosecutors.

Federal prosecutors in New York also said Friday that Cohen was directed by the president to pay off two women who claimed to have had affairs with Trump in order to prevent negative press coverage, violating campaign finance law in the process.