[goingoren]

♠8
♥KJ53
♦ K8742
♣ JT7

My partner opens 3c, RHO passes. Would you raise to 4c here?

[Bbradley62]

Probably, although form of scoring and vulnerability might matter.

[aguahombre]

If partner's 3C bids look like 3C bids, we should always raise to 4C in this situation. It just works; and we don't need to know why it will work in this case; just do it.

We don't need to worry about colors or form of scoring. Partner's 3C opening took that into account already.

[dkham]

4♣ from me

[helene_t]

Yes.

You can apply the law of total tricks:

If partner has 7 clubs, you have 10 together so you should compete to at least the 4-level (ten tricks). Even if he has 6 clubs, he won't have more than 3 spades so opps have a 9-card fit. This means that you shouldn't allow them to play at the 3-level.

The worst case scenario is that he has 3 spades and 6 clubs so there are only 18 tricks. If opps can make 3♠ you will be one down in 4♣. If they double you and you are vulnerable that is not good. Or they can make 11 tricks. In that case you can make 7 tricks so 4♣X is too expensive unless the vulnerability is favorable. BUT:
- Partner probably has 7 clubs if you are vulnerable.
- Partner's long clubs in combination with you singleton suggest that there may well be a trick more than the law predicts.
- If opps can make exactly 10 tricks (or 12) you are fine anyway.
- Opps don't always make the right decision. The more aggresively you bid the bigger the chance that they get it wrong.

It may well be right to bid 5♣, or to psyche a 3NT bid, or maybe sometimes to pass (opps will think you don't have club support when you pass and that sometimes misleads them). What certainly can't be right is first to pass and then bid 4♣ next round. If you delay your raise you make it easier for opps to make the right decision.

But the normal bid is 4♣.