Ben Curtis fired a second-round five-under-par 67 to take the clubhouse lead with Trahan and Davis Love III at the Arnold Palmer Invitational.
Curtis started with two bogeys, but recovered well, hitting five birdies in seven holes between 10 and 16, to sit on seven under for the tournament.
He was joined by Trahan who shot a 68 and Love III who had a 71.
Love III had perhaps the most bizarre round of the day with seven birdies, including three in a row at 15, 16 and 17, and six bogeys.
Two more Americans, Kevin Na and Phil Mickelson, and South Africa’s Retief Goosen were a shot further back.
Mickelson and Goosen both fired 67s, the former’s round featuring an eagle on the par-four eighth, and Na a 70.
Ernie Els and Heath Slocum were both well placed, the South African six under through 14 and the American six under through 12.
World number two Steve Stricker had to make do with a 71 to sit four under at the halfway stage.
JB Holmes, who held a share of the lead after the first day, was enduring a tough second round, though, as he sought a top-four finish which would keep his chances of securing a place at the Masters alive.
The American double-bogeyed the seventh and 13th to leave him two over for the round and four under overall after 14.
Colin Montgomerie fired a 71 to sit one under overall, but England’s Justin Rose could only manage a 73 to go with his opening-round 75 to lie four over and looks set to miss the cut.