In a Senate floor speech responding to Schumer, McConnell made it crystal clear that he is not inclined to call in witnesses -- but he didn’t rule it out either.
“If they fail, they fail,” McConnell said of the House’s efforts to make a clear case against the president. “It is not the Senate’s job to leap into the breach and search desperately for ways to “get to guilty.’” That would hardly be impartial justice,” he said.
“We don’t create impeachments,” McConnell said. “We judge them.”
Sarcastically calling the House Democrats’ work the “most rushed, least thorough, and most unfair impeachment inquiry in modern history,” McConnell urged the House to “turn back from the cliff” and not impeach the president.
McConnell slammed his Democratic counterpart for short circuiting the “customary and collegial process” in laying down the basic groundwork in determining the process and procedures for a potential impeachment trial.
“The preferable path would have been an in-person conversation, which nonetheless, I still hope to pursue,” McConnell said.
Later in the day, McConnell doubled down and declared he will not be an impartial juror during the trial.
“This is a political process, there's not anything judicial about it," he said during a press conference Tuesday afternoon. "Impeachment is a political decision, the House made a partisan political decision to impeach. I anticipate we will have a largely partisan outcome in the Senate. I'm not impartial about this at all."
Democrats have criticized McConnell in recent days for promising to work in “total coordination” with the White House, accusing him of allowing the president to plan his own trial.
Schumer, in a letter addressed to the McConnell on Sunday, asked to hear from four witnesses during the Senate’s impeachment trial – acting White House chief of staff Mick Mulvaney, former National Security Adviser John Bolton, Associate Director for National Security at the Office of Management and Budget Michael Duffey, and senior adviser to the acting White House chief of staff, Robert Blair – all of whom refused to participate in the House investigation.
"I did not hear a single sentence, a single argument as to why the witnesses I suggested should not give testimony. Impeachment trials, like most trials, have witnesses. To have none would be an aberration. Why is the leader, why is the president so afraid of having these witnesses come testify?" Schumer said Tuesday on the Senate floor in direct response to McConnell.
“If we don’t have them, the trial won’t be fair,” he said.
"The leader seems obsessed with speedy and wants to throw fair out the window," Schumer added.
Schumer said that some Republican senators have privately told him that while they believe the charges against the president are serious, they haven't seen enough evidence to make a decision - which is why he wants to haul in witnesses with direct knowledge as to why aid was withheld from Ukraine.
"That's one of the reasons I've proposed subpoenas for the witnesses and documents, all directly relevant from officials who have yet to testify under oath during any stage of the house process," Schumer said.
"Senators who oppose this plan will have to explain why less evidence is better than more evidence," he said. "Again, let me say that. To every senator in this room, Democrat and Republican, senators who oppose this plan will have to explain why less evidence is better than more evidence, and they're going to have to explain that position to a public that is understandably skeptical when they see an administration suppressing evidence and blocking senior officials from telling the truth about what they know."
Schumer suggested he could force votes on the matter. It would take 51 votes in the Senate - or a simple majority - to approve motions on witnesses on the floor when the time comes.
"We will have votes on whether these people should testify. And whether these documents should be made public and part of the trial, and the American people will be watching. They will be watching," Schumer said.
"The American people have a wisdom that seems to be lacking with some of my colleagues. That a trial without witnesses is not a trial. It's a rush to judgment. It's a sham trial. The American people understand that a trial without relevant documents is not a fair trial. Again, a desire not to -- not for sunlight but for darkness," Schumer added.
Senate Republicans, coming out of a caucus lunch with Vice President Mike Pence and White House Legislative Affairs Director Eric Ueland, hinted Tuesday that they believe the Senate's potential impeachment trial is likely to begin Jan. 6.
"The date was discussed in terms of when we would probably take it up, which is January 6. Other than that it was mostly this discussion of whether or not there would be witnesses called," GOP Sen. Mike Braun of Indiana said.
When the Senate's No. 2 Republican John Thune of South Dakota was asked if Jan. 6 was the start date, he responded "probably."
Another Republican in leadership, Sen. Roy Blunt, said that McConnell told the conference that he thinks he and Schumer will be able to agree on a date by the end of this week.
On Pence's message to Republicans during lunch, Braun told reporters that Pence was "mostly talking about all the good things we've done and to stay strong and get through the process, [but] nothing particular on any type of strategy or tactics."
Earlier in the day, McConnell called Schumer’s requests a “fishing expedition,” and blasted him for taking the opposite position during former President Bill Clinton’s impeachment trial in 1999.
“Very tellingly,” McConnell said, “our colleague from New York completely omits any motions to dismiss the case like the one he was happy to vote for himself as a new senator back in 1999,” referring to Schumer’s vote to dismiss the charges against Clinton.
“But now the same process that Senator Schumer thought was good enough for President Clinton, he doesn't want to afford president Trump. Go figure,” McConnell said.
McConnell called the House impeachment inquiry “woefully, woefully inadequate” and blamed Senate Democrats for trying to do “House Democrats’ homework for them.”
“The Senate is meant to act as judge and jury to hear a trial, not to rerun the entire fact-finding of the investigation because angry partisans rushed sloppily through it,” McConnell said.
McConnell concluded his remarks by saying he wants the Trump impeachment trial to mirror the Clinton impeachment trial, which would call for the Senate to pass two resolutions to set the ground rules. The first resolution would sketch out the basic things like scheduling, opening arguments, and the timing of motions.
The second resolution, McConnell said, would offer more details about the latter half of the trial, including whether any witnesses would be called.
“The answer is the House should not impeach on this basis in the first place. But if the House plows ahead, if this ends up here in the Senate, we certainly do not need jurors to start brain-storming witness lists for the prosecution and demanding to lock them in before we have even heard opening arguments,” McConnell said.
GOP Sen. John Kennedy, R-La., also took a moment to slam Schumer for his list of demands related to the impeachment trial.
"For him to suggest if we don't do what he's suggesting that we're trying to hold a rigged proceeding, that's pretty rich coming from Chuck in light of what his colleagues did in the House," Kennedy said after the Republican caucus luncheon. "That's like being called ugly by a frog. I'm not saying Chuck's a frog. I don't think they have frogs in Manhattan."
"Based on what I know today and what others know today, I think this thing is dead as fried chicken in the Senate," Kennedy said of the impeachment trial.
ABC News' Trish Turner contributed to this report.