Democrats are keeping their collective eye on the prize as the Trump Senate impeachment threatens to inch closer in the coming weeks.

On Monday,  Minority Leader Sen. Chuck Schumer (D-N.Y.) sent a letter to senators outlining specific documents he believes should be requested as part of the process. The letter specifically outlined recently unredacted Ukraine-related emails from the Office of Management and Budget. In addition, Schumer is asking for four witnesses, including  White House Chief of Staff Mick Mulvaney and former national security adviser John Bolton.

Senate Majority Leader Mitch McConnell (R-KY) has stayed in Republican rank pushing for a short trial with the demand that the Senate agreement should wait until after the initial stages of the proceedings, citing the 1999 Clinton impeachment as an example of precedent.

Schumer is fighting back.

“In 1999, the Senate could not reach an initial agreement on witnesses because a number of Senators on both sides of the aisle, including then-Majority Leader Lott, believed that the facts in the Clinton case had been fully established before the trial,” Schumer wrote in his letter. “The House Managers’ proposed witnesses had already testified multiple times under oath, and transcripts of their testimony were available to the Senate.”

According to Schumer, the Trump case is different because “the President has ordered that witnesses with direct knowledge, and documents containing directly relevant evidence, be withheld.”

The Senate is scheduled to return to session on January 3, 2020.

Read his letter here.

Watch the video below via NBC News’ Hans Nichols.