why not have one rep switch parties for a day?
Because there are only 19 Repubs and 20 are need to have a quorum.
It is a matter of total number there, not which party. :)
“why not have one rep switch parties for a day?”
It’s not a matter of that! They need a quorum to hold a vote. There are only 19 Rs. They need 1 more person. They could all change parties for a day, and it wouldn’t make any difference! They need one more body!