Padraig Harrington shot a three-under second-round 69 to continue his strong start to the Houston Open.
In the final event before next week's Masters, the Irishman produced a mixed round but an eagle and five birdies left him on seven under.
American Chris Kirk is the leader on nine under, a shot ahead of compatriots Anthony Kim and Johnson Wagner.
English world number two Lee Westwood fired a par 72 to remain four under, alongside Phil Mickelson.
Westwood, 37, made a poor start to his round, dropping three shots on the back nine as he carded four bogeys and a birdie.
However, he rallied on the way home to claim three birdies on the front nine to salvage par.
He is joined on four under by Mickelson, who continued his warm-up for the defence of his Masters title with a second successive round of 70, and Italian Francesco Molinari, who shot a 71.
Ross Fisher's 70 meant he reached the halfway point on three under, two strokes ahead of compatriot Brian Davis and South African Ernie Els.
Harrington's round was a mixed bag, with only one shot dropped in his opening nine holes - at the 14th - but then a hat-trick of bogeys from the second, only to salvage some pride with an eagle at the par-five eighth.
With the Masters on the horizon, the Irishman said he hoped he could ride the current wave of European success, with the world's top four players all being Europeans.
"European golf is very strong and I'm delighted to see it," he said.
"Obviously I've got to improve on my own game and what I'm doing, and I fully believe I'm going to play the best golf of my life going forward.
"Obviously I had a peak in 2007, 2008 there, and I believe that there's more good stuff to come. But those results were obviously really good, plus I definitely feel like I'm a better player now than I was in 2007, 2008. I'm looking forward to good things happening."
Defending champion Kim had an erratic day, recovering from inaccurate tee shots with fine putting and bunker shots to record eight birdies, and end the day just one shot off the pace.
"It helps a lot knowing I played well before, knowing I made a couple putts when it mattered and hit some quality golf shots when it did mattered really helps, especially since I won here in college about six, seven years ago," he said.
"Some shots I had are similar, some putts I had are very similar, so I try to remember those things and play off that."