A former senior Senate Republican aide who helped win the Supreme Court confirmations of Chief Justice John Roberts and Associate Justice Samuel Alito Samuel AlitoREAD: Supreme Court justices mourn death of Ginsburg, 'an American hero' Ginsburg death sets up battle over future of court Trump's Supreme Court list reveals influence of Clarence Thomas MORE on Sunday urged Senate Republicans to allow witnesses at President Trump Donald John TrumpUS reimposes UN sanctions on Iran amid increasing tensions Jeff Flake: Republicans 'should hold the same position' on SCOTUS vacancy as 2016 Trump supporters chant 'Fill that seat' at North Carolina rally MORE’s impeachment trial.

“The historic norm is to call witnesses in Senate impeachment trials, even or especially after rushed House jobs. Senate Rs -- You guys can do this. You don’t have to vote to convict and remove; but you should want to know the full story here,” tweeted Gregg Nunziata, a longtime Senate aide who is well known in conservative legal circles.

“The Founders are pretty clear -- the House process is about an 'accusation', the Senate process is about a trial on the merits,” Nunziata said in a follow-up tweet.

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The former staffer, who is now a partner at Manatt, Phelps & Phillips LLP, made his public comments shortly after news broke that former national security adviser John Bolton John BoltonDiplomacy with China is good for America The Hill's Morning Report - Sponsored by The Air Line Pilots Association - Pence lauds Harris as 'experienced debater'; Trump, Biden diverge over debate prep DOJ launches probe into Bolton book for possible classified information disclosures MORE has written an unpublished manuscript in which he claims Trump told him he wanted to freeze $391 million in military assistance to Ukraine until Ukrainian officials there agree to investigate Democrats including former Vice President Joe Biden Joe BidenMomentum growing among Republicans for Supreme Court vote before Election Day Trump expects to nominate woman to replace Ginsburg next week Video of Lindsey Graham arguing against nominating a Supreme Court justice in an election year goes viral MORE.

Nunziata formerly served as the chief nominations counsel on the Senate Judiciary Committee and also as general counsel and senior domestic policy adviser to Sen. Marco Rubio Marco Antonio RubioSunday shows preview: Justice Ginsburg dies, sparking partisan battle over vacancy before election Florida senators pushing to keep Daylight Savings Time during pandemic Hillicon Valley: DOJ indicts Chinese, Malaysian hackers accused of targeting over 100 organizations | GOP senators raise concerns over Oracle-TikTok deal | QAnon awareness jumps in new poll MORE (R-Fla.).

It’s a sign that Republican senators are likely to hear growing calls across the political spectrum to extend the impeachment trial, despite clear indications from many GOP lawmakers including Senate Majority Leader Mitch McConnell Addison (Mitch) Mitchell McConnellMomentum growing among Republicans for Supreme Court vote before Election Day Trump expects to nominate woman to replace Ginsburg next week Video of Lindsey Graham arguing against nominating a Supreme Court justice in an election year goes viral MORE (R-Ky.) that they would prefer to wrap the proceeding up as quickly as possible.

The report by The New York Times has roiled the debate over whether senators should vote to subpoena additional witnesses including Bolton and acting White House chief of staff Mick Mulvaney Mick MulvaneyMick Mulvaney to start hedge fund Fauci says positive White House task force reports don't always match what he hears on the ground Bottom line MORE.

Senate Minority Leader Charles Schumer Chuck SchumerVideo of Lindsey Graham arguing against nominating a Supreme Court justice in an election year goes viral Graham signals support for confirming a Supreme Court nominee this year Pelosi orders Capitol flags at half-staff to honor Ginsburg MORE (D-N.Y.), Speaker Nancy Pelosi Nancy PelosiSunday shows preview: Justice Ginsburg dies, sparking partisan battle over vacancy before election Trump is betting big on the suburbs, but his strategy is failing 'bigly' Trump orders flags at half-staff to honor 'trailblazer' Ginsburg MORE (D-Calif.) and the House impeachment managers pounced on news that Bolton is prepared to publish an account directly tying Trump to the effort to pressure Ukraine to investigate Biden and his son Hunter Biden.

“It’s up to four Senate Republicans to ensure that John Bolton, Mick Mulvaney, and the others with direct knowledge of President Trump’s actions testify in the Senate trial,” Schumer said in a statement.

Pelosi tweeted “the refusal of the Senate to call for [Bolton], other relevant witnesses, and documents is now even more indefensible.”