At 9-under-par, Nelson leads Dave Stockton and Jim Thorpe by one shot. Chuck Moran is two off the lead at 7-under.
Nelson, who won his third event of the season last week, carded six birdies and three bogeys in the second round. After birdying the par-5 3rd, Nelson bogeyed the 4th and 5th holes. Nelson came back with birdies on the 7th, 11th, 14th and 15th holes, before dropping his third shot of the day at the par-3 16th. But in a roller coaster round, Nelson finished on a high note with a birdie at the 17th.
Stockton made a bid for his first Senior Tour victory since the 1997 Franklin Quest Championship by shooting a 6-under-par 66. The 58-year-old Stockton posted six birdies and no bogeys in the second round.
Sixty-year-old George Archer matched Stockton for the round of the day. Archer, who shares the course record with a 64 in 1998, reeled off eight birdies and two bogeys for a round of 66. Archer, who won the season-opening MasterCard Championship, is at 5-under-par, four shots off the lead.