Here’s their proposal in The Hill:

To avoid that predicament, Pelosi and McConnell should jointly create a neutral referee to advise them, starting on Election Day, about any vote counting disputes that might arise once the polls are closed and the tabulating of ballots begins. In 2018, we saw some alarmist rhetoric over the normal process of counting the provisional and absentee ballots while preliminary tallies were being verified. Were that same agitation to occur in 2020, a neutral referee to counsel the congressional leaders could help calm a jittery atmosphere and prevent partisan suspicions from spinning out of control. If, based on the advice of their neutral referee, Pelosi and McConnell jointly announce the election over, then as a practical matter it is.

We have thoughts on how to pick a neutral referee. Pelosi and McConnell could each choose one member of a panel of three people, and their two choices could pick the third. This approach, modeled after private sector arbitration, is the simplest method for finding an umpire whom both sides can accept as fair. Minnesota has used a version of this approach to settle some contentious statewide elections.

But whatever method of selection Pelosi and McConnell prefer, their chosen umpire should be ready before counting ballots begins. They should also pledge to accept the findings of the neutral arbiter unless both agree otherwise, a commitment that maintains the bipartisanship of their arrangement. They could make this commitment formal by putting it into legislation, but that step is unnecessary. As long as these two leaders stick to this deal, they can achieve the closure needed for a successful inauguration.