smerriman, on 2020-July-27, 19:43, said:
You lead from AKxxx, and see xxx in dummy. When partner has xx, which 'vast majority' of cases do you not want to give him a ruff?
It is when partner plays low with both xx and xxx, as per your suggestion, when you completely lose, since you can't "try for a ruff anyway" without setting up declarer's queen for free in the latter case.
This one is a somewhat bad example as you gave leader too many cards, though I guess it depends on how high your spots are compared to dummy's spots. In this case if partner has 3 declarer's Q will drop. The main problem here is whether you need to lead the third round of the suit (hoping partner ruffs declarer's J winner), or if partner will follow with the J and declarer ruffs, in which case you might have missed a tempo to do something else that was necessary.
Better example is perhaps something like holding AKTx with xxx in dummy. If partner has Jxx, you definitely need to get him in to lead through to take 3 tricks in this suit. But if partner has 2, it might be necessary to give him a ruff here to collect 3 tricks.
Or maybe AKxxx with dummy Jxx. If partner has doubleton, ruff is often necessary else declarer scores a trick eventually. But if partner has 3 small, trying to play a 2nd round would drop declarer's Q and establish the J for a pitch somewhere which could often be bad, you have to switch and set up your winner elsewhere before declarer sets up the J himself.