A close decision

A BJ for BR1 is surely no different from any other win, whereas a BJ is BR2's only hope, other than a swing (which I think is reflected in your calculation that arrives at 78%).

But of course you might not get a stiff on LH-1. 79% is the worst your chances could be. (78% in the version refined to account for a BR2 BJ). It might be helpful if I substitute this 78% figure into my formula -

21% + ((100% - 21%) * 78%) = 83%

That's accounted for in my 21% figure for the chance of winning by a swing (win or push) on LH-1 (assuming I got it right).

 

I'm basically out of this for discussion purposes. However, I was wondering if London Colin and Monkeysystem can arrive at probabilities they both agree on?