Thanks to a birdie at the 18th, Sposa has sole possession of the 36-hole lead at the Greater Greensboro Chrysler Classic.
Sposa stands at 10-under-par through two rounds, one-shot clear of 18-hole leader Scott Simpson, who followed an opening 66 with a 3-under-par 69.
Five players share third place at 8-under-par, including Scott Hoch (68), Jeff Maggert (67), David Berganio, Jr. (66), Omar Uresti (65) and Rich Beem (65).
Defending champion Hal Sutton (71) is seven off the pace at 3-under-par.
Sposa, who has never finished better than seventh in a PGA Tour event, recorded seven birdies and one bogey in the second round to move to the top of the leaderboard.
The last time Sposa was close to this position was in the 2000 Westin Texas Open, where he was a co-leader after a first-round 64, but failed to break 70 over his remaining three rounds to tie for 48th.
Certainly in my mind, Im ready to win out here, said Sposa. I dont want to play to keep my card. I want to win and I want people to know who I am. Im not going to be intimidated by the chance to win. Im playing for that chance.
While Sposa vies for win No. 1, Simpson is in search of victory No. 8, but his first since the 1998 Buick Invitational.
Its been so long since I have been in contention maybe it would be good for me to try to visualize winning, said Simpson, who missed the entire 2000 season due to a right ankle injury.
If his first-round 66 was like a dream, Simpson was shaken awake quickly on Friday. The 45-year-old bogeyed two of his first three holes, but responded with five birdies for his second-straight sub-70 round.
My son was kind of excited for me, said Simpson, who won this event and the U.S. Open in 1987. Dad is usually such a dork, but he actually had to say, Geez dad, good playing. That was kind of neat.
Sposa started the day two shots back of Simpson and quickly made up ground by birdieing his first two holes. Two more birdies at the 9th and 13th holes, both par-5s, gave Simpson a share of the lead for the first time at 9-under.
Following a routine two-putt par at the 14th, Sposa added another birdie to his card at the par-5 15th.
Leading by one at 10-under, Sposa missed the green at the par-3 17th. A bad lie led to a poor chip, which resulted in a bogey.
Unfazed, Sposa stuck his approach shot on the par-4 18th to three feet, and then tapped in the birdie to finish the day in double digits.
The 30-year-old Sposa is in his third full season on the PGA Tour. The past two years, he failed to break the top 125 on the money list and resorted to earning his card through Q-School.
Im just trying to stay real calm and not get ahead of myself, said Sposa, who is expecting his second child in a couple of weeks. Ive been out here for three years now, so I know this thing is so far from over that for me to start talking about victory speeches would be ridiculous.
Full-field scores from the Greater Greensboro Chrysler Classic