All three games in round 4 of Reggio Emilia finished with winners and losers. Alexander Morozevich entered the round in clear first, but ended it in third after being outplayed by Vassily Ivanchuk. Ivanchuk built up a winning attacking position with White in a Ruy Lopez, and while the game got murky for a while he never really let Morozevich get back into the game. In a pleasant rarity, Morozevich let Ivanchuk deliver mate - very sporting of him!
That put Ivanchuk into the lead, and he was joined there by Hikaru Nakamura. Anish Giri's 23.d6 was interesting at best and dubious at worst, and the follow-up 31.Qd5? left him with a lost ending. Nakamura won pretty easily after that, and he looks poised for a second strong result.
Finally, Nikita Vitiugov's loss to Fabiano Caruana resembled Giri-Nakamura. Like Giri, Vitiugov embarked down an enterprising sacrificial path, but like Giri he played without sufficient energy, only to wind up in a hopeless ending down material.
After four of ten rounds, Ivanchuk and Nakamura have 8 points (they're using 3-1-0 scoring), a point ahead of Morozevich. Caruana has 4, and Vitiugov and Giri are bringing up the rear with 2 points apiece.
The games, with my (light) comments, are here.