(CNN) Senate Majority Leader Mitch McConnell is expected to move quickly to acquit President Donald Trump if a closely watched vote planned for Friday to compel witnesses and documents for Trump's impeachment trial is defeated, according to Sen. John Thune of South Dakota, who is the number two Senate Republican.

The discussions come as Republican leaders believe they are closing in on the votes necessary to block any witnesses, a move that would bring a swift end to the trial.

"In the end it's going to be up to the leader, but my view would be at that point you would want to start bringing this thing to a conclusion," Thune said Wednesday. "I'm not sure there would be any value or any point in keeping it going."

Thune noted that after the question of witnesses is resolved, the organizing resolution for the trial allows for an open-ended number of procedural motions to be made by senators, something that might slow a quick end to the trial, especially if Democrats demand a series of debates and votes on motions.

Each motion is debatable for two hours, as are any amendments to them, according to Alan Frumin, a former Senate parliamentarian.

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