Multi 2 diamonds, or simply Multi, is a contract bridge convention whereby the opening bid of 2♦ shows multiple types of hands, which always includes a weak-two bid in either major suit, while the additional meaning may be a strong balanced hand (commonly 20-21 high card points), or a 20-22 three suiter. The inherent ambiguity as to both suit and strength makes it a powerful and popular convention capable of seriously disrupting the opponents' bidding.
Although it's technically a brown sticker convention (since no long suit is initially known), its popularity and availability of defenses persuaded World Bridge Federation to allow its usage on tournaments of lesser ratings. It is described in WBF Convention Booklet.
An opening bid of 2♦ classically shows one of four types :
- Weak two in a major suit (6-11 HCP)
- A strong balanced hand of a defined range
- Strong three-suited hand
- An ACOL 2 type ; typically in a minor
Often the convention is played with only one of the strong options being present, i.e. a three-way bid. As long as at least one strong option is present, the multi 2♦ opening is a forcing bid. More recently a trend has been seen to play a "hearts only multi" in which the weak 2 option is always hearts. "Spades only multi" also presumably exists. The first response assumes that opener has a weak two in a major.
Another popular innovation is the 'mini multi', which contains no strong option. This variant is actually less legal (i.e. legal in fewer tournaments) than the traditional multi. This may seem odd, but there is a logical explanation. The reason is that the ambiguity inherent in a multi opening is a double edged sword - it can cause more problems for the pair using it than for their opponents (typically when the multi opener has a strong hand and his partner has support for both majors). This risk is no longer present when using the mini multi.
Responding to the multi:
Assuming his left hand opponent passes, the partner of the multi opener is forced to bid. He has several options available:
2♥: this is a Pass or correct bid typically showing a hand with no support (two or fewer cards) for hearts and no interest in game.
2♠: this is also a Pass or correct bid, which shows no support for spades but guarantees at least three card support for hearts.
3/4 ♥/♠: these bids extend the principle of the previous two, showing progressively greater levels of support for the majors. For example, 3♠ would show three card support for spades and four card (or longer) support for hearts. Not all pairs allow these higher-level responses to the multi because they can cause problems if opener has one of the strong hand variants.
2NT: Forcing, asking opener to clarify his hand. This bid will be used with stronger hands than those above, where opener is interested in bidding game on the basis of High card point strength rather than having a good fit.
Opener's rebids:
With type (1):
Over 2/3/4♥: pass or bid ♠at the appropriate level;
Over 2/3♠: pass or bid ♥at the appropriate level;
Over 2NT several schemes exist for answering:
Scheme 1:
bid 3♣ to show hearts, upper range or type 4 with clubs;
3♦ to show spades, upper range or type 4 with diamonds;
3♥ or 3♠ with lower range.
Scheme 2, first variant (not playable if type 4 hands are possible):
bid 3♣ to show hearts, lower range;
bid 3♦ to show spades, lower range;
bid 3♥ or 3♠ with upper range.
Scheme 3, second variant:
bid 3♣ or 3♦ as in first variant;
bid 3♥ to show spades, upper range;
bid 3♠ to show hearts, upper range.
Scheme 4 (PLauken), second variant:
bid 3♣ to show upper range, unknown suit;
bid 3♦ to show hearts, lower range;
bid 3♥ to show spades, lower range.
With type (2):
rebid in notrumps at minimum level
Other rebids show type (3) and should be specified on the Convention card.
There are various popular defenses to the multi. The method outlined below is not necessarily the best from a technical point of view, however it is perfectly adequate and has the advantage of being easy to remember.
Double shows a balanced hand with 13-15 HCP or any hand with 19+ HCP, with the range being clarified by subsequent bidding (the hand will usually pass if it has the lower range or bid again with the higher).
2♥ and 2♠ are natural, showing 5+ cards in the suit bid and good opening bid values
2NT shows 16-18 HCP and a balanced hand.
Other bids are generally strong (16+ HCP) following the principle that if the opponent's bid is weak, our bid should be strong.
In general, when defending against a multi one should assume that the multi bidder has one of the weak options for his bid, since they occur much more frequently than the strong ones. It is also important to bid aggressively on the first round of bidding after the multi has been opened, before the opener's partner knows what type of hand he has.
