Northern Irishman Graeme McDowell holds a three-stroke lead at the halfway stage of the World Challenge in California on Friday, while Jason Day endured a nightmare round to drop down to last place. McDowell, a winner of the event two years ago, birdied his opening three holes on track to a six-under 66 second round at the Sherwood Country Club. The 2010 US Open winner began the second round two shots behind overnight leader Nick Watney but is well placed at nine-under overall, three shots clear of American trio Bo Van Pelt (68), Jim Furyk (69) and Keegan Bradley (69). Five-time World Challenge champion Tiger Woods is a further shot back at five under. Despite birdying four of his five holes from holes nine to 13, Woods finished with a three-under 69. Day began the day in a tie for 10th place, but fell to 18th after a three-over-par 75 that included two double bogeys on the back nine. Rickie Fowler and Watney are in a share of sixth position. Fowler, who has two top three placements during 2012 including victory at the Wells Fargo Championship, posted an eagle and four birdies on his way to a round of five-under 67. Joining Fowler at four under is Watney, who endured a difficult day on the green. The 2012 Barclays champion was Thursday&aposs pacesetter but fell away in round two as he carded a one-over 73. Jason Dufner shot a four-under 68 to claim sole possession of eighth place at three under. Dustin Johnson enjoyed a bogey-free round, ending the day tied for ninth alongside Matt Kuchar. Johnson managed four bogeys on Thursday but responded with a faultless four-under 68 second round, while Kuchar posted a three-under 69. Brandt Snedeker (68) and Webb Simpson (73) are eight shots adrift of McDowell. Zach Johnson (70), Steve Stricker (71) and Hunter Mahan (73) ended the day at even par, while Englishman Ian Poulter (72) was joined by Bubba Watson (74) at one over.