https://www.republicanleader.senate.gov/newsroom/press-relea...
He’s basically that the partisan makeup of the Senate as of the most recent election should be the controlling factor.
It has the veneer of a neutral rule, and that’s all they need.
you forgot "and is after 1890" since he is ignoring the contradictory cases before then.
He tweeted it today
https://mobile.twitter.com/senatemajldr/status/1307121192516...
(Not saying you're wrong. If I repeat something, I like to have direct sources)