It's simple
Under the rules the Senate has chosen to run this peach mints trial, no witnesses will be called.
To change that rule, a majority of Senators must vote to change the rule. That means 51 must vote to change the existing rule.
As usual, lyin' Chuck Scumbag keeps asserting that the vote is about blocking witnesses. He's implying that Senate R's are voting to BLOCK what the Senate would do by default. That's why he's trying to confuse things regarding a tie vote.
And it will work. If there's a tie, shills will spew that a Republican hardliner Judge joined with Hardline Republican Senators to BLOCK witnesses
Hopefully it won't be a tie, but this is the bullshit construct Chuck Scumbag is building to muddy the waters.
It also brings judiciAl appointments front and center for electioneering.