gnasher, on 2011-January-16, 00:55, said:
If I were going to raise spades, I'd do so by bidding 4♦, which in my world shows support and a singleton, so I'd consider that.
In practice, though, it's very unlikely that partner has a purely natural, forcing 3♠ bid - even if it's a real suit, he will probably have a heart fit. Rather than bury us in 4♠ or 5♥, I'd like to give partner a chance to show his heart fit. 4♦ accomplishes that, so that's what I'd choose.
The other actions I'd consider are pass and 4♥.
I worry a bit about this "very unlikely" principle. If I open 1NT and partner transfers to spades, he is very unlikely to have a six card club suit as well, but so what? He may have, and you do not assume he has not.
When I open 3
♥ naturally, it is pretty unlikely, perhaps very unlikely, that partner has a game force, a spade suit and no heart fit, but again so what? He may have, and I see no reason to bid as though he has not because it is very unlikely.