Hallo,
sorry, but just on the surface this doesn't
seem right.
for instance, a run-of-the-mill no-cycle Condorcet
case (actually it was IRV and the Condorcet winner
did not win) would be the Burlington 2009 election
most of us are familiar with. in that case M=5.
now if you picked k=3 and chose candidate A to be
Kurt Wright (who was the plurality winner and neither
the IRV winner nor the CW), there is a set of (k-1)
candidates (those would be Smith and Simpson) that
Wright beat consistently. yet he is not the overall
winner.
you can go to the Warren Smith page or i can scarf
up the numbers from the defeat matrix again.
how am i reading this wrong?
For k=3, this criterion says that, when a candidate
wins every 3-way election, then this candidate should
also be the overall winner.
So to be able to apply this criterion to Kurt Wright,
he would also have to win a 3-way election between
himself and (say) Montroll and Kiss.
Markus Schulze