According to the rules of the game, the right to select the first card to play (the opening lead) belongs to the defenders; afterwards, the right to lead belongs to the hand who has won the previous trick. Being on lead generally presents an advantage, as it presents an opportunity to choose a suit and card which will develop a trick for the leader's side. However, in endplay situations being on lead certainly does not present an advantage—quite the opposite.
The tempo can be used for many purposes:
- Setting up tricks – for example, against notrump contracts, defenders will often lead the longest and strongest suit, to set up the tricks in that suit. Against trump contracts, lead of a short suit can set up a subsequent ruff before the declarer can draw trumps.
- Pitching losers – for example, having x opposite AKQx, the declarer may discard cards from another suit on the honors, holding xxx opposite xxx if on lead; if the opponents were on lead, they can cash the tricks in the declarer's weak suit.
- Taking tricks – the converse of pitching losers. Having the lead lets us take our tricks before the other side gets to pitch in the suit(s).
- Trump promotion or coup en passant – if the other side had the lead, they could simply draw trumps; however, with our side on lead, an extra trump trick can be produced.
- Killing entries – opponents can be forced to use entries in the wrong order.
|Example 1||♠||A K Q J|
|♦||x x x x|
|♣||x x x x|
|♠||x x x x||
|♠||x x x x|
|♥||x x x x||♥||x x x x|
|♦||A K Q J||♦||x|
|♣||x||♣||A K Q J|
|♥||A K Q J|
|♦||x x x x|
|♣||x x x x|
In this extreme example, whoever leads first will take the first 8 tricks, regardless of the denomination. That means that neither side can make any contract, and every contract will fail by at least two tricks—the advantage of having on opening lead makes a three-trick difference.
South in 4♠
|♠||J 10 7 5 4 2|
|♦||A Q 3|
|♣||J 7 6|
|♥||A K 8 4||♥||7 6 5 3|
|♦||8 5 2||♦||K J 10 4|
|♣||K 7 5 4||♣||10 8 3 2|
|Lead: ♥A||♠||A Q 8 3|
|♥||Q 10 9 2|
|♦||9 7 6|
Keeping initiative—gaining tempo—by not taking a finesse can be decisive to prevent the opponents from developing defensive tricks.
Against South's 4♠ west leads the ♥A (indicating the king) and continues with the ♦8. The opening lead, although natural, was unfortunate, as it gave the declarer a tempo to develop heart tricks for himself. However, it is now essential not to take the diamond finesse so as not to lose tempo. South must take the ♦A and play to the ♠A, again refraining from finessing. Now, the declarer can lead hearts for ruffing finesse and discard diamonds until West covers with the ♥K, then ruff and cross over to ♣A, again refusing to finesse. On the remaining hearts, all diamonds including the queen are discarded. In total, the declarer loses one trick in trumps, hearts and clubs each.
Note that a diamond opening lead sets the contract, as it doesn't give the tempo in hearts to the declarer: the declarer must lose a heart and two diamonds before he sets up the hearts for diamond discards; the trump king is the fourth trick for the defense.