how come no one mentions the fact that, most of the time, the declarer has a two suiter on this auction? by two suiter i mean at least 5/4 , and the rest of the time he has 6+ spades therefore, i would not consider opening a blank ace as criminal in this particular situation, with two ideas in mind 1) avoid to lead his likely second suit, i.e. diamonds or 2) get super lucky and hit my partner s single or Kx if the suit i pick is declarer s side suit, or even grab our four possibles tricks when he had possible pitches. of course, all that is very speculative, but leading a trump or a diamond looks scary to me, anyway scarier than an ace. also, there is a miniclue in the fact that rho did not try to find a possible 4/4 fit in hearts, so my definitive choice would be club ace.