Senate Majority Leader Mitch McConnell (R-Ky.) dismissed Minority Leader Chuck Schumer's (D-N.Y.) call to have four White House witnesses testify in the Senate's likely impeachment trial, arguing that it's the House's "duty to investigate" and that the Senate will not volunteer its time for a "fishing expedition."

"We don’t create impeachments, Mr. President. We judge them.

"The House chose this road. It is their duty to investigate. It's their duty to meet the very high bar for undoing a national election. As Speaker Pelosi herself once said, it is the House’s obligation to, quote, 'build an ironclad case to act.'

"If they fail, they fail. 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."

— Sen. McConnell

Context: In a letter to McConnell Sunday night, Schumer proposed that the Senate issue subpoenas for documents related to the Trump administration's decision to freeze military aid to Ukraine, as well as the following witnesses:

White House acting chief of staff Mick Mulvaney

Mulvaney adviser Robert Blair

Former national security adviser John Bolton

Office of Management and Budget official Michael Duffey

The big picture: McConnell, who rebuked Schumer for sending a letter that was leaked to the press rather than waiting to meet in person, rejected the notion that it is the Senate's obligation to call new witnesses — even those like the above White House officials who have defied subpoenas in the House impeachment inquiry. He also criticized Democrats for failing to pursue the subpoenas in court, calling it a "rushed process."

Axios' Jonathan Swan has reported that McConnell plans to hold a short, possibly two-week trial with no new witnesses — and that President Trump has largely come around on the plan.

McConnell has faced intense backlash from Democrats for stating on Fox News that he will closely coordinate with the White House on the Senate trial and that there is "zero chance" Trump will be removed from office.

Before beginning an impeachment trial, Senate rules dictate that senators must swear an oath to do "impartial justice according to the Constitution and laws."

The other side: House Democrats argue that enforcing subpoenas for officials like Mulvaney and Bolton would take months to litigate, as it has for former White House counsel Don McGahn. They claim that impeachment is a matter of urgent concern because Trump's conduct poses an ongoing "threat to our election's integrity."

Responding to McConnell's comments, Schumer said on the Senate floor that McConnell has offered no "specific reasons" for why the witnesses he's asking for should not be heard.

"Each witness we named was directly involved in the events that led to the charges made by the House. ... Senators who oppose this plan will have to explain why less evidence is better than more evidence."

What to watch: McConnell and Schumer still have to meet officially to discuss the layout of the trial, but Schumer said in his floor speech that he will bring votes on specific witnesses. 51 senators are required to call a witness, meaning only a few GOP defections would be necessary.

Go deeper: Inside the McConnell-Trump impeachment trial playbook