House Judiciary Committee Chairman Jerrold Nadler accused Senate Republicans of violating their oath to be impartial jurors in an impeachment trial, as GOP senators defended their right to work for President Donald Trump's acquittal.

Senate Majority Leader Mitch McConnell, R-Ky., said last week that he was working in "total coordination" with the White House - something Nadler, D-N.Y., characterized Sunday on ABC's "This Week" as akin to "the foreman of the jury saying he's going to work hand in glove with the defense attorney."

"That's in violation of the oath that they're about to take, and it's a complete subversion of the constitutional scheme," Nadler said.

Senators take an oath to "do impartial justice" at the start of any impeachment trial - but several Republican senators argued that impartiality doesn't cover politics.

"I (have) clearly made up my mind. I'm not trying to hide the fact that I have disdain for the accusations in the process," Sen. Lindsey Graham, R-S.C., said Sunday on CBS's "Face the Nation."

Graham called "this whole thing" a "crock" and warned that Democrats were "weaponizing impeachment."

"I want to end it. I don't want to legitimize it," he said.

"Senators are not required, like jurors in a criminal trial, to be sequestered, not to talk to anyone, not to coordinate. There's no prohibition," Sen. Ted Cruz, R-Texas, said on "This Week," calling impeachment "inherently a political exercise" and Trump's impeachment a "partisan show trial."

Sen. Rand Paul, R-Ky., speaking Sunday on CNN's "State of the Union," also argued that there was nothing wrong with senators having already made up their minds. Calling impeachment an effort to "criminalize politics," he noted that "we're going to hear the evidence repeated, but we're not going to hear any new evidence."

Senate GOP leaders have been telling allies that they want to limit the trial to a short proceeding, omitting any witnesses from testifying. That isn't sitting well with House Democratic leaders, who contend that senators should use their trial to secure evidence and testimony that the White House prevented House investigators from accessing.

"They don't want the American people to see the facts," House Intelligence Committee Chairman Adam Schiff, D-Calif., said Sunday on ABC, appearing alongside Nadler.

"They realize that what's been presented in the House is already overwhelming, but that there's more damning evidence to be had," Schiff continued. "I hope that the senators will insist on getting the documents, on hearing from other witnesses, on making up their own mind, even if there are some senators who have decided out of their blind allegiance to this president that he can do nothing wrong."

Nadler added that senators should "demand the testimony" of people like Secretary of State Mike Pompeo, acting White House chief of staff Mick Mulvaney and former national security adviser John Bolton, "who at the president's instruction have refused to testify."

There are some Senate Republicans who want to hear from witnesses at the trial. But they aren't thinking about Pompeo, Mulvaney and Bolton; they're thinking about the whistleblower and Hunter Biden.

"You can be sure we're going to allow the president to defend himself," Cruz said, adding: "That means, I believe, if the president wants to call witnesses, if the president wants to call Hunter Biden or wants to call the whistleblower, the senate should allow the president to do so."

Hunter Biden, son of former Vice President Joe Biden, sat on the board of Ukrainian energy company Burisma for five years and was paid as much as $50,000 a month, despite having no expertise on the subject matter. As Democrats have made the case that Trump tried to use his office to pressure a foreign leader into announcing investigations against a political rival, several Republicans have rallied around the countercharge that Trump was right to be concerned about "corruption" involving the Bidens - though it does not appear that Joe Biden, who was closely involved in Ukraine policy, made any decisions to advantage the company.

"I love Joe Biden, but none of us are above scrutiny," Graham said Sunday, noting there were "legitimate concerns" about Hunter Biden's activity. But he added that the Senate could look at all of those issues - as well as whatever new information Trump's lawyer Rudy Giuliani unearthed in his latest trip to Ukraine - "after impeachment" and should move ahead without witnesses.

It is not clear whether the senate will be forced to hold separate votes on witnesses - or if most of the GOP would hold rank in that situation. It takes 51 senators to approve a motion. There are 53 Republicans in the Senate, meaning the GOP can afford to lose no more than two senators on any motion for McConnell to fully control the course of the trial.

Paul guessed that, ultimately, two Democratic senators would end up joining all Republicans in voting to acquit Trump, just as a handful of Democrats are expected to join the GOP in the House to vote against impeachment.

Paul did not say who those two Democrats might be. At this point, some Democratic senators are taking pains to avoid committing to vote to convict the president, even if they are otherwise echoing House Democrats' frustrations with the president's actions.

Sen. Sherrod Brown, D-Ohio, said on "State of the Union" that Trump "did things Richard Nixon never did." But he hedged when asked whether Trump's transgressions rose to the need for removal, noting that senators should make that decision "based on the evidence."