Carlsen has 7.5 points (+4,=7), ahead of Vladimir Kramnik 7 (+3,=8) and Levon Aronian (+4,-2,=5). Svidler (+2,-2,=7) is in fourth.
Kramnik and Carlsen are the only unbeaten players. Only the trio at the top have plus scores. Interestingly, everyone has won at least one game. The biggest disappointment has been Vassity Ivanchuk, who has had terrible time management.
Extrapolating from a statistical analysis and Monte Carlo simulation by Jeff Sonas, Carlsen has something like a 72 per cent chance of becoming the challenger. Aronian has white against Kramnik in Round 12. The previous five games between the leading trio have been indecisive though Kramnik came very close to winning against Carlsen when the Russian had white.
Both Aronian and Carlsen have had their share of luck. This is part and parcel of taking calculated risks and neither has toned down his style. Kramnik has been more solid as always. Aronian has lost twice, when Boris Gelfand and Svidler got on top.
Despite the generous prize money of over euro 500,000, this is one tournament where rating points and second place don't really matter. GM John Nunn predicted early on that the challenger would likely be decided in the very last round and it could be headed that way if all three maintain form.
Carlsen may throttle back a bit since his primary task now would be to avoid losing. If he's cold-blooded enough to make three draws, it may be good enough. On the other hand, he's naturally aggressive and he finishes against the out-of-form Ivanchuk, Teimourn Radjabov and Svidler and he might fancy his chances of winning two of those three games.
Kramnik may go into "special gear" at this stage, throwing caution to the winds as he sometimes does, when the chips are down. Aronian is not really capable of toning down his creative style and he is likely to up the risk-taking as well to try and grab as many wins as possible.
The DIAGRAM, WHITE TO PLAY, (Kramnik,Vs Radjabov, Candidates 2013), is near-equal in objective terms but white has more active pieces and there are several concealed tricks. Play continued 28.Rb6 Qxa2 ? In hindsight, 28.-- Rc7 29. Rxa6 Nd7!? may be ok for black since 30. Nxe7+ ? Rxe7 is winning for black. Also 28.--a5 is defensible.
Now white wins with 29.e5 Nd5 30.Rb2 Qa4 31.Bxd5 Rxd5 32.Rb4! Qa2. The queen no longer defends e8 so 33.Nxe7+ Kh8 34.Nxd5 Qxd5 35.Qc4 Qxc4 36.Rxc4 Bxe5 37.Kf1 (1-0). The pin will lead to lines like 37.--Re6 38. Rce4 Bc3 39. Rxe6 fe6 40. Rxe6 when white is easily winning.
Devangshu Datta is an internationally rated chess and correspondence chess player