Scott's fellow countryman Jason Day made it a four-way tie at the top with an opening 12 foot birdie putt, while Donald was only four back when he picked up shots at the first and short seventh.
Westwood was on the same mark after making a curling 15 footer at the fifth, but McIlroy wasted an opening three with a bogey six at the second, rated the easiest hole on the course.
Westwood made another two from almost 50 feet at the seventh and when he rolled in a 12 footer three holes later he was six under, joint seventh and only two back.
Donald had his first bogey of the week on the tenth, though, to go back to three under, one better than McIlroy.
Laird, married in a kilt in Colorado last Saturday with Day and Nick Watney among the guests, said: "I came into this week feeling fresh and on a high. Sometimes it's amazing when you have no expectations how well you'll play."
Westwood undid a lot of his good work by missing the green at the 13th and making a mess of his chip, then going in two bunkers and horse-shoeing out for a second successive bogey.
He returned to four under, one in front of Donald and McIlroy and still only four off the lead with Day bogeying the tenth, before making birdie two holes later to rejoin Scott, Fowler and Moore.
Phil Mickelson holed out from 128 yards for an eagle two on the 11th, but promptly double bogeyed the next to drop back to two under.
Day remained eight under with two to go and was part of a five-way tie as US PGA Tour rookie Keegan Bradley was eight under as well after a 65.
Westwood dropped another shot at the last after going long into sand and so had played the final six in four over to be only two under.
Donald's much more solid 69 took him into the third round on three under and McIlroy was alongside him with one to play.