WASHINGTON (Reuters) - U.S. Senate Majority Leader Mitch McConnell on Tuesday sought to slam the door on further investigations of President Donald Trump by declaring “case closed” after a two-year probe of Russia’s meddling in the 2016 elections, even as House Democrats’ war with the White House intensified.

McConnell, the top Republican in the U.S. Congress, delivered a stinging rebuke of Democrats seeking additional information on Special Counsel Robert Mueller’s report that found no evidence Trump’s 2016 campaign colluded with Russia.

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“The special counsel’s finding is clear. Case closed,” McConnell declared.

Meanwhile, battles between the White House and congressional Democrats over documents and testimony related to the Mueller investigation deepened on Tuesday.

White House Counsel Pat Cipollone informed the House Judiciary Committee in a letter that ex-White House Counsel Don McGahn does not have the legal right to comply with a House of Representatives subpoena and disclose documents related to Mueller’s investigation.

White House spokeswoman Sarah Sanders, when asked by ABC News whether McGahn would comply with the subpoena, said, “I don’t anticipate that that takes place.”

McConnell accused Democrats of being in an “absolute meltdown” and refusing “to accept the bottom line conclusion” that Mueller’s “exhaustive” report found no collusion with Russia.

Since the public release of the report last month, House and Senate Republicans have defended the president and called for an end to congressional investigations.

Mueller detailed extensive contacts between Trump’s campaign and Moscow. His 448-page report also outlined 11 instances in which the president tried to impede the special counsel’s investigation, but avoided a conclusion on whether or not Trump obstructed justice.

Speaking on the Senate floor after McConnell, Senate Democratic Leader Chuck Schumer fired back, calling Trump a “lawless president” and accusing the Senate Republican leader of wanting to bury any congressional investigations.

“Of course he wants to move on. He wants to cover up,” Schumer said of McConnell.

Schumer likened McConnell’s move to President Richard Nixon, who was under investigation by Congress before resigning from office in 1974 in the face of impeachment and likely conviction.

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“It’s sort of like Richard Nixon saying let’s move on at the height of the investigation of his wrongdoing,” Schumer said.

While McConnell urged an end to the fight over the Mueller report, he acknowledged that was unlikely. Democrats hold a majority in the House, while Republicans control the Senate.

“Would we finally be able to move on from partisan paralysis and breathless conspiracy theorizing? Or would we remain consumed by unhinged partisanship,” McConnell said, adding, “Regrettably, the answer is pretty obvious.”

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House Democrats prepared to meet with Justice Department officials on Tuesday over Attorney General William Barr’s failure to release the full unredacted Mueller report as they prepared to cite him for contempt.

The House Judiciary Committee has scheduled a Wednesday vote on a contempt citation for Barr, who missed a second deadline to give lawmakers the full report and failed to appear at a hearing before the panel last week.

The full House would then vote on the rebuke.

A contempt citation against McGahn or other administration officials could lead to a civil case, raising the possibility of fines and even imprisonment for failure to comply.

The Judiciary Committee is among several House panels investigating Trump and his administration on various matters, including the Russia probe and Trump’s personal and business tax returns.

The administration is stonewalling congressional investigators while the president, who has denied any wrongdoing, vowed to fight all congressional subpoenas.

On Monday, U.S. Treasury Secretary Steven Mnuchin turned down the House Ways and Means Committee’s request for Trump’s tax returns, teeing up a likely legal battle.

Democratic lawmakers want Mueller to testify before Congress, something Trump has balked at although Barr has said he would not object.

If lawmakers decide that Trump obstructed justice by seeking to impede Mueller, Judiciary Committee Chairman Jerrold Nadler could move to impeachment proceedings against the president.

If the House goes down the impeachment route, at least some Republican support would be needed for a Senate conviction.