Chad Campbell surged to the top of the leaderboard at the RBC Canadian Open after the Texan fired a nine-under-par 63 at Glen Abbey.
His bogey-free, nine-birdie round allowed Campbell to leap up to first place and reach 14-under 130 at the halfway mark.
Campbell has not won a tournament since 2007, when he landed the last of his four PGA Tour victories at the Viking Classic in Mississippi.
Harman went round in 67, Wagner took route 66, and Hearn enjoyed an immaculate 64.
Graeme McDowell, the only Irish competitor in the field, failed to make it through to the weekend action after finishing on three over. The 35-year-old carded a 72 after registering a round of 75 in his opening round.
There was no U-turn from Australian Robert Allenby, who carried out his pledge to withdraw from the tournament after sacking caddie Mick Meddlemo midway through the first round following a disagreement over club selection.
Allenby said on Thursday he would not play on and was true to his word.
His countryman Jason Day was back in contention towards the top of the leaderboard.
After going close at last week's Open Championship, Day posted a 66 to reach 10 under.
Ricky Barnes made a 70 which meant he survived with comfort on six under overall, with the American's round notable for the hole-in-one he achieved at the fourth hole, winning him a BMW for his efforts.