Phil Mickelson has positioned himself to win his first British Open, shooting a 5-under 66 that sent him to the clubhouse with a three-stroke lead.

Given the testy conditions Sunday at Muirfield, that should be good enough.

Five shots behind Lee Westwood at the beginning of the day, Mickelson matched the best round of the tournament and moved to the top while the other contenders faded away.

Westwood is 3 over through 15 holes and three shots behind Mickelson, essentially needing to birdie out just to force a playoff. Adam Scott briefly grabbed the outright lead, but three straight bogeys finished off his hopes.

When Mickelson rolled in a 10-footer at the final hole for his fourth birdie in the last six holes, the celebration was on. He pumped his fists while his caddie broke down in tears of joy.