This is an attempt to narrow the 5-9 range of the normal 1 Major - 2 Major sequence. After a 1 opening, playing Constructive raises,
- responder shows the 5-7 range by first bidding 1NT forcing then rebidding 2.
- He shows an 8-9 range by directly bidding a constructive 2. The disadvantage to this method is that opener cannot know, after a 1NT response, whether the 2 bid is simply a preference with 2, or a 'real' minimum raise with as many as 4 spades.
Why NOT To Play Constructive Major Raises
There are two reasons not to play this popular convention. One of them is constructive and the other is competitive.
The constructive reason is that auctions often go faster than expected and it might not be a good idea to make an ambiguous bid at a high level. Let's say you respond 1NT to partner's 1 opening with QT8-J-J8765-J754 because the hand is just too wimpy to justify a simple raise. Maybe you have an agreement that 2 shows substantial values or maybe you just don't want to get partner all excited with your scattered five HCP. You can go back to SPADES later and partner will know that you have a weaker hand than a smple raise. Actually, and this is one of my objections, partner doesn't know anything of the sort. You could also have K6-KQT7 -J98-T876 which is plenty strong enough for a simple raise but a completely different type of hand. Partner will probably be OK passing either bid but he might have a problem and the opponents might give him a worse problem by bidding.
Besides that problem, you could also have QJ8-AKT6 T6- 9754 and respond 1NT because the hand is too good for a single raise. After all, you are going to jump in Spades (or raise Hearts) on your next turn. Partner will not be confused between these two raises. However, partner could cross you up by raising 1NT to 3NT. Yes, that does show a very good hand. Partner might have slam interest opposite the 3 card Limit Raise but will not want to get beyond game opposite the weaker hand. However, the only logical thing to do with either hand over 3NT is to correct to 4. 4 might seem useful on the stronger hand as an advanced cue. However, you then need to be insured against ever holding a hand like 8-KJ87654-QT65-T8 since that hand should call 4 over 3NT. The 3NT rebid is not the only fast auction that can cause you trouble on these hands. There are several others, although most are not as bad as the raise all the way to 3NT. In its own way, the raise to 2NT is just about as bad. Is a correction to 3 of the Major super-weak or is it the card. Limit Raise? If the former, we will have to use up all our bidding room with the 3 card Limit Raise by going to four. If the latter, how do we bid the wimp hand? Well, I raise 1 to two in the first place whenever I have less than limit raise strength and three cards in support. Simple but it seems to work OK. If you never eschew the simple raise out of weakness, partner has fewer ambiguous sequences to deal with. Partner will know that you will make a simple raise whenever you have one and he or she can count on you for either fewer trumps or more points if you don't.
The competitive reason behind playing wide-ranging single raises (wrsr) is that it makes it harder for the opponents to find their fits and easier for our side to compete (or decline to compete.) Say your LHO opens 1, your partner passes and your RHO bids 1NT and you haveA6-T65-K5-KQT965. You have a fairly simple 2 bid. If LHO has a great Club holding, you are still at the two level and besides, RHO, with QT8-J754-J8765- may feel that his or her fit for partner would preclude passing the penalty Double. and that is probably true. However, you have been warned about the stack. Also, RHO may not have the hand to Double and your partner may be able to raise. So RHO, who felt too weak to bid at the two level, will now either have to compete at the three level or never show support for opener's suit. Given the same hand, you hear LHO open 1 and RHO raise him to two. You have to bid this hand at any but unfavorable vulnerability. You have a six-loser hand with opening strength, three quick tricks and you really want that Club lead. However, you are a level higher and they have know about their fit; they will Double you and sit for it when it is right and compete when they should. If it is right to compete to 3 or higher, you will be able to do so but so will the pair that faced the lesser challenge of a 1NT response. On the hands where the opponents should not compete to 3 , despite responder's fit, responder is not usually going to be able to avoid showing his fit and the opponents' chance for a plus score, or a bigger plus score is gone..