McDowell rises to challenge
Graeme McDowell hit the round of the day to go three shots clear at the World Golf Challenge in California.
The Northern Irishman, who was in a chasing pack of three after a first-round 69, signed for a six-under 66 to move to nine under overall.
He kicked off with three successive birdies and added four more in the back nine to weigh against a solitary dropped shot at the par-four seventh.
American trio Bo Van Pelt, Jim Furyk and Keegan Bradley are tied for second on six under, with the latter making a bogey-free round including three birdies.
Host Tiger Woods lies one stroke further back after signing for a 69 - dropping shots at eight and 15 either side of four birdies in five holes.
Australia's Jason Day is bottom of the 18-man field on two over through 36 holes, with the third and final non-American, England's Ian Poulter, also struggling on one above par.
Overnight leader Nick Watney slipped back to five shots off the lead after following his day-one score of 67 with a 73.
Bradley, who has spoken up on several occasions for those who use so-called 'pivot points' with long putters, was quizzed about the joint proposal by USGA and Royal & Ancient to outlaw the technique from 2016 at the end of his round.
He revealed he had received abuse for his favoured putting stroke on Twitter and called for a greater empathy from those within the game.
"I've been catching such flak on Twitter and these other places and it would be good to kind of quiet them a little bit. I had a guy telling me to send my application in to Burger King for 2016," he told reporters at the event.
"I hope that people look at us - guys who use a long putter or belly putter - for the accomplishments and the players that we are, not look at us for using an unconventional putter.
"I feel like the USGA has really put an 'X' on our back and really shone a light on us, and I don't know if that's exactly fair.
"When we started putting with it, they were legal, and they still are. It's a sticky situation, and I hope people can see through that."