Well, you need 60 votes. Please explain how they could have gotten 60 votes when there are not 60 pubbies?
Couldn’t be simpler. you take 10 remotely conservative Repubs each with a briefcase. In those briefcases is $10M in cash each temporarily borrowed from some of the conservative donors.
Each Pub meets with one endangered Democrat and explains to them that that 10M will be spent on their opponent and lawyers, and that Mitch is completely unaware of the proceedings. You then simply close the briefcase and walk away reminding them that caucusing with the GOP on the PP matter solves many mutual problems and that 9 other Dems are currently in an identical meeting and if word gets out, money gets spent.
Then return the cash to the donors and get on with defunding PP.
Simple. Legal. People fund opposition every day.
Rare moments of weakness from semi-ethical dems.