Senate Minority Leader Chuck Schumer (D–New York) wants to make President Donald Trump’s imminent trial in the Senate a full exploration of the president’s conduct. Schumer has penned a letter to Senate Majority Leader Mitch McConnell (R–Kentucky), asking him to include acting White House Chief Of Staff Mick Mulvaney and former National Security Adviser John Bolton as witnesses in the Senate trial.

Besides these two high-profile figures, Schumer says the Senate Democrats would also like to call Mulvaney’s aide Robert Blair and Office of Management and Budget official  Michael Duffey as witnesses.

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It’s extremely unlikely that the Senate Republicans would vote to subpoena those witnesses without approval from the White House. In cooperation with the White House, the Senate Republicans might seek to call their own preferred witnesses.

Schumer has proposed that the trial process commence on January 6. He wants the trial itself to begin on January 9. He has said that he wants a framework akin to the impeachment trial of former President Bill Clinton in 1999.

“The trial must be one that not only hears all of the evidence and adjudicates the case fairly; it must also pass the fairness test with the American people,” Schumer says in the letter to McConnell. “That is the great challenge for the Senate in the coming weeks.”

McConnell and Schumer have not had a discussion about the trial parameters. After a deal is struck, the Senate’s impeachment resolution governing the rules could pass with broad support.

McConnell’s spokesman Doug Andres has clarified that McConnell would comment only after he spoke to Schumer.

“Leader McConnell has made it clear he plans to meet with Leader Schumer to discuss the contours of a trial soon. That timeline has not changed,“ Andres said on Sunday night.

If McConnell can get 51 of the 53 Senate Republicans to stick together, he could ignore Schumer’s request and scrap bipartisan negotiations altogether.

Republican senators like Sen. Mitt Romney (R–Utah) and Sen. Susan Collins (R–Maine) would be tough for both parties to persuade. A simple majority is needed to pass resolutions in the Senate trial. Convicting and removing the president requires a vote of two-thirds of senators.

For now, Senate Republicans have settled on a strategy of hearing the opening argument from Trump and House Democrats, with the option to call witnesses later.

Schumer has disagreed with the Senate Republicans and has said that witnesses, documents and trial parameters “should be considered in one resolution.”

McConnell told Sean Hannity on Fox News last week that he was in close coordination with White House Counsel Pat Cipollone about the trial. He also said that Trump has asked for witnesses such as Hunter Biden to appear before the trial.

Schumer also proposed “that the Senate issue subpoenas for a limited set of documents that we believe will shed additional light on the administration’s decision-making.” Finally, Democrats want 24 hours for both the president’s lawyers and the House impeachment managers to each give “opening presentations and rebuttals” to the Senate, along with 16 hours of questioning by senators, divided equally between the parties. Witnesses would be questioned for four hours per side; in Clinton’s trial, however, witnesses gave closed-door depositions.

Schumer said he hoped he and McConnell could help the Senate “rise to this critically important occasion.”