Wyndham Clark holds a four-shot lead at US Open halfway mark, with Rory McIlroy faltering after a 71 back nine. Mixed form defined day two, as Clark's 69 (64-69) set a US Open record 14-under 70, while McIlroy's triple bogey on 15th dropped him to even par. *Context*: Tight conditions at Shinnecock Hills saw only 10 players under par, with Xander Schauffele and Matt Fitzpatrick tied at three-under.

Clark's record-breaking pace (lowest 36-hole US Open score at Shinnecock) contrasts with McIlroy's meltdown: three birdies, three bogeys, and a double bogey on the back nine. *Backstory*: McIlroy briefly challenged Clark at the turn (33) but unraveled with distance errors, calling it "tough" wind conditions. Bryson DeChambeau missed cut for third major, while Scottie Scheffler (68) lurks at par.

Schauffele (66) and Fitzpatrick (69) push Clark, with Dustin Johnson lurking two back. *Season implications*: Scheffler seeks career Grand Slam; Clark aims to dethrone 2023 champ. Collin Morikawa (65) and Sam Stevens (69) round out top five.

Who will win? Clark's composure under pressure and record pace make him favorite, but McIlroy's resilience and Scheffler's major pedigree keep race tight. Live coverage continues Saturday on Sky Sports.