Yes, it's a bad pun, and yes, I know the "j" in Sergey Karjakin's name is pronounced like a "y". I'm sticking to the dumb pun anyway. Who'd have thought that Karjakin, -2 after four rounds, would lead the tournament eight rounds later? What's that, you say, he's only tied for first? Incorrect. By beating "co-leader" Fabiano Caruana, Karjakin has the better tiebreaks, and given the tournament rules it means he would win the event if it finished right now. (Just as Magnus Carlsen advanced and Vladimir Kramnik didn't when they finished London 2013 with the same number of points.)
Amazing. Karjakin has won four games in seven rounds, going from worst to first, and for the moment he has the pole position for a second straight title tilt with Magnus Carlsen. With White against Caruana and the latter's Petroff, Karjakin avoided nonsense like 5.Qe2 and went for the main lines, choosing 5.Nc3. After 10.a3 and 11.Nd4 there was a new position on the board, and it seems that he obtained an advantage. The critical idea that probably won him the game, and possibly a second shot at the title, was 17.Bxd5, sacrificing the exchange for a pawn and a nuclear bishop on d5, radiating power in every direction. Caruana didn't manage to cope with this piece, and by the time Karjakin picked up a second pawn for the exchange on move 31 Black's position was hopeless.
Caruana's loss could have been Shakhriyar Mamedyarov's gain. Like Caruana, he had been undefeated all tournament long and had been in first or just half a point behind for a long time. Had he won with White against Ding Liren, he'd have been in sole first. Even a draw would have been acceptable: he'd have been in a three-way tie for first, and then he'd have been ahead on tiebreaks given his plus score against Karjakin and even record vs. Caruana. If, if, if. Ding didn't lose, and despite drawing all 11 of his games up to this point he didn't split the point either. Instead, he won, and now he's even with Mamedyarov, half a point behind the leaders.
Ding took a page out of Kramnik's book (why not? Everyone else copies his openings) and played the Semi-Tarrasch. He equalized, and when Mamedyarov pushed to create a kingside attack Ding was able to push his queenside majority, make a second queen, and win.
So four players lead or are within half a point of the lead. Did I say four? Make it five: we shouldn't forget Alexander Grischuk. If had defeated Levon Aronian he'd have been in the tie for first. He had a big chance on move 23, but rejected it for some reason and Aronian escaped with a draw. Still, Grischuk is within half a point of Karjakin and Caruana, so with two rounds to go more than half of the field still has a great shot at winning the tournament.
The last game featured two players who are out of the running. Vladimir Kramnik had a winning advantage against Wesley So, but for the umpteenth time in the event left half a point (or more) on the table, and the game finished in a draw.
The games (with my notes) are here. Sunday is a rest day, and the penultimate round will be played on Monday, with these pairings: