Irwin, winner of the 1997 and 1999 3M Championship held in Minneapolis, is in position for victory No. 3 this week at the new TPC of the Twin Cities.
Irwin shot a 4-under-par 68 to tie Jose Maria Canizares for the 36-hole lead at 8-under-par 136.
Bruce Lietzke made his first career hole-in-one on the Senior PGA Tour Saturday en route to shooting 66 and tying overnight leader Mike McCullough for third place at 6-under.
Bruce Fleisher (67) and last weeks winner Bobby Wadkins (68) are tied for fifth place at 5-under.
Irwin is in search of his third win at this event and his third victory overall this season. Saturday, he carded five birdies and one bogey.
Canizares earned his maiden tour triumph in March at the Toshiba Senior Classic. The Spaniard climbed the leaderboard in the second round by recording eight birdies and two bogeys.
McCullough, a two-time winner in 2001, parred his first 10 holes in the second round before birdieing the 11th and 12th holes. He went on to add one more birdie to his card, but also notched a trio of bogeys on Nos. 13, 15 and 16.
Full-field scores from the 3M Championship