He might know that it only takes 51 senators to change the rules of the senate - not 67.
Yes, the so called nuclear option on cloture and filibuster or rule changes. It only requires a simple majority, which is why after the Democrats did this under Harry Reid as majority leader at the time, it than allowed Mitch and the Republicans to give them what they deserved after the Democrats first opened pandoras box of a 51 vote simple majority. So, now we have two conservative SCOTUS appointments and @180 new Federal judges. Which is why Mitch can change the Senate impeachment trial rules with a 51 simple majority vote and get the trial done quickly.