When my partner calls trump and the dealer is on my right and has the right bower, should I still lead trump knowing we can't get that trick?
Your best bet is to lead trump to your partner in this scenario
Think about this from your partner's point of view. What would they play if they had the lead? They ordered up the right bower, so they must have a pretty solid hand in that suit. What is their plan for making three tricks, knowing that one is guaranteed lost to the right bower? Probably it involves some variation of outlasting the dealer in the trump suit. The biggest threat to that plan is that the dealer somehow manages to win a trick with a little trump that they might be holding. If that happens, then the defense has two tricks, and the final trick is likely to be an off-suit trick that could go either way. Therefore, if your partner had the lead, they would likely play their highest trump to try to force the right bower out, and you leading trump to them is the next best thing.
If you lead trump, and your partner plays their highest trump (which I'm kind of assuming is the left bower, if they ordered up the right), then the dealer has two choices. They can either throw off a small trump, which helps eliminate your biggest worry, which was that they might have found a way to make that small trump good. More likely, they will overtrump with the right, which means your partner will be playing last on the next trick. That gives your partner the possibility of discarding a loser if you are winning the trick, or winning it with a low trump if you're not, and they're void in the lead suit.
The only scenario here that is not too good is if the dealer leads an off-suit card, you're not able to win in that suit, and your partner is forced to follow suit. However, if that's how the cards were dealt, then that play is bound to happen eventually because the dealer is guaranteed a trick from the right bower. To avoid it you would have to find an opportunity for your partner to discard their loser, and there is no safe way to do that with you in the lead.
Both of the alternative plays suggested in the comments seem more risky. Consider the options:
- Play a side ace (if you have one): If either of your opponents is void in the suit of your ace, this will give them a chance to make good on a low trump, or at least force your partner to burn a trump to save the trick. It also doesn't buy you that much because if the dealer is holding that suit, there's a reasonable chance that they will play it when they win the lead with their bower. So, you're risking giving away a trick in exchange for the possibility of winning a trick that you could have won through less risky play.
- Lead low and hope to cross-trump (if you have a void): As before, this creates opportunities the defense to make good on a low trump, or worse, an off-suit card. On top of that, there's a good chance your partner ends up having to spend a trump to take a trick where neither of the opponents played any trump. It's particularly bad if each of the opponents has a low trump, because then they might be the ones cross-trumping. Leading trump ensures that if both of your opponents have trump, then they will at least collide on the first trick.
In summary, leading trump is likely to call out the dealer's right bower on the first trick, and put your partner in a good tactical spot for the second trick. To me, that's less risky than any of the options for an off-suit lead.
Here's another perspective on the matter that leads to the same conclusion: https://members.tripod.com/~Borf_Books/ecolum31.htm#leadtrump