1 Club - 1 Heart - 1NT
Check the first article in this series here. We still have some loose ends to deal with in regards to the 2 Clubs invitational bid.
One of them requires a small digression about the principles of natural bidding. In a 5-card majors, strong NT system, which is the most common natural system nowadays, we open a balanced hand too weak for a NT opener with 1 in a minor suit. The most popular way to play that (and certainly the one I would assume if I were playing without discussion with anyone) is one in which we open 1 Club with 3-3 in the minors, "regardless" of suit disparity (that "regardless" should be taken with a grain of salt, depending on position at the table and other factors). This means that 1 Diamond will only deliver 3 cards when opener has the specific distribution 4=4=3=2; all other balanced hands opening 1 Diamond will have at least 4 cards there.
1 Club, therefore, is opened with all 4333 hands without 4 diamonds. That leaves a point of contention in the bidding 1 Club - 1 Heart: how many clubs do we require for rebidding 1 Spade when we have 4 of them? There are 3 possibilities:
a. Rebid 1 Spade whenever you have 4 spades, including the 4=3=3=3 hands.
b. Require at least 4 clubs for rebidding 1 Spade; meaning, the 4=3=3=3 hands rebid 1NT.
c. Require at least 5 clubs (or a 3-suiter) for a 1 Spade rebid; any balanced hand rebids 1NT, regardless of how many spades it has.
All are playable, and have staunch defenders among the top players. You and your partner have to pick one of them. I will not dissect the pros and cons of each choice right now. Why is this relevant for our discussion about 2-way checkback Stayman? Because it decides whether spades are still a live suit after the bidding starts 1 Club - 1 Heart - 1NT.
If you picked option (a), in which 1NT denies spades, spades can no longer be a trump suit unless responder has 5 of them. You can still play 1 Club - 1 Heart - 1NT - 2 Spades as a natural reverse, showing 5+ hearts and 4+ spades (you will rebid spades with five). This is a game force, as any reverse by responder in natural bidding, and it takes away some of the weight of the artificial 2D bid over 1NT.
You still have to decide what to do with 1C - 1H - 1NT - 2C - 2D - 2S. The natural meaning of this would be a 4-4 hand in the majors, very concentrated in spades, i.e., a hand that supposes that a 2 Spade contract in a 4-3 fit would be a better spot than 2NT, if opener rejects the invitation. Note that this would deny 5 hearts, since the odds of 2 Hearts being better than 2 Spades when responder has 54 are too great for you to go through that sequence with 5 hearts and 4 spades. (Of course you may have AKJ9 in spades and 86543 in hearts, in which you may decide to treat your hearts as a 4 card suit... we never advocate turning off your common sense).
That meaning is natural, easy to remember, but perhaps too rare. If you want to play around with other possible meanings, how about using that 2 Spades bid as an invitation (following the general principle), but with a 3-suiter, short in opener's suit? This allows you to find a diamond contract after the 1C-1H-1NT start, which is rather difficult using natural methods. And you can still stop in 2 Spades if opener judges it best, perhaps with a 3=2=3=5 hand.
If you picked (b) or (c), above, spades are a possible trump suit. In those cases it is better to keep the natural meaning of the bids: 1C-1H-1NT-2S natural GF reverse, 1C-1H-1NT-2C-2D-2S invitation with (exactly) 44 in the majors. With 54 in the majors, you invite via 1C-1H-1NT-2C-2D-2H, and if opener accepts the invitation he bids 2S whenever he has 4 cards there. This option shows rather more about opener's hand than we would like when there is no spade fit lurking, but there's is no other solution -- if you want to play in spades, you must bid them. It is the biggest downside of picking choices (b) or (c) -- the difficulty of finding a spade fit after a 1NT rebid. (The upside, information-wise, is that opener does not show he has spades in an auction such as 1C-1H-1NT-3NT).
If the opening bid was 1 Diamond, following the principle of only opening 1 Diamond with 3-cards with 4=4=3=2, any rebid other than a raise in hearts denies 3 diamonds. So, in effect, you can bid 1D-1H-1S promising 4+ diamonds. You must discuss with your partner whether you are showing an unbalanced hand or you may still be balanced when you bid 1 Spade (you are actually picking between options (b) and (c), since (a) becomes impossible). Your 2 Spade rebid (whether after 2C-2D or directly) then has the meaning described in the last paragraph.
I know I promised to deal with 1 minor-1 major-1NT-2 Diamonds in Part 2, but we had to take care of this issue before going there. Here is the following article in the series.