Had Viswanathan Anand defeated Vladimir Kramnik in today's action he would have been at least a pretty decent favorite to win the Candidates' tournament, even at this early stage. That was never in much danger of happening, however. Kramnik had Black, yes, but he was prepared to the gills in a Vienna Variation Queen's Gambit and drew in 30 moves without ever leaving his prep. So Anand remained half a point in front of Kramnik.
Anand could have been caught by Peter Svidler, had he managed to win with Black against Levon Aronian. After some long preparation in a Gruenfeld (nowadays that goes without saying) a position arose where Svidler was up a piece for a pawn, but Aronian had a mighty center and enduring play against Svidler's king. Svidler had the chance to steer the game to an easy draw, but with some justification and ambition he went for more. On this occasion, that hope went unrewarded. Aronian negotiated the complications better than his opponent, and when Black returned the piece the result was a terribly passive ending where Aronian would surely break through sooner or later. He did, and leapfrogged Svidler in the standings. Aronian is tied with Kramnik for second place, and they play in round 5.
Veselin Topalov drew his fourth straight game, this time in an English against Sergey Karjakin. Neither player was ever close to getting an advantage, and the play remained pretty calm throughout.
Finally, Shakhriyar Mamedyarov escaped the cellar by defeating Dmitry Andreikin and putting him there instead. Mamedyarov generally had the better of the play in an offbeat Chebanenko Slav, but only managed to win when Andreikin blundered with the unnatural 37...Kf7.
The games, with my light comments, are here, and here are tomorrow's pairings, with player scores in parentheses: