Carlos Franco, Mark Hensby and Mike Heinen finished in a tie for third place at 14-under-par 202.
After the second round was completed Saturday morning following Friday's bad weather, Slocum found that a 64 he shot the day before was good enough to secure the 36-hole lead at Omni Tucson National. However, at a single shot, Slocum's advantage was sure to be tested in the third round.
Baddeley began the day six shots off the pace and picked up his first birdie of the day at the par-5 second. The Australian then kickstarted his ascension up the leaderboard with three consecutive birdies starting at the par-4 fifth to move to 10 under.
The young Australian added a birdie at the 10th and grabbed a share of the lead at minus-13 with a birdie at the par-3 12th.
Baddeley, who is seeking his first career victory on the PGA Tour, made it two in a row with a birdie at the par-4 13th. He then birdied the par-5 15th en route to a bogey-free round and a share of first place.
Slocum, also in search of a breakthrough victory, found trouble early with a bogey at the par-5 second.
The 30-year-old recovered with a birdie at the par-3 fourth and matched Baddeley in the lead with back-to-back birdies from the par-4 ninth.
Slocum regained the outright lead at 16 under with a birdie at the par-4 16th but the Nationwide Tour product faltered with a bogey at the last to fall back into a tie for first.
Per-Ulrik Johansson found himself battling for the lead until a late mistake left him two shots off the pace.
The Swede jumped out of the gate with an eagle at the second but stumbled two holes later with a bogey at the fourth.
Johansson caught fire on the inward half with four birdies before stepping onto the 18th tee. The 37-year-old walked away with a double bogey on the closing hole to complete a round of 69.
Johansson joined Vaughn Taylor and Bill Glasson in a tie for sixth at 13-under-par 203.
Harrison Frazar and Dan Olsen were one shot further back at 12-under-par 204.
John Daly continued to struggle on Saturday. After an opening-round 67, Daly, who earned his first PGA Tour victory in nine years two weeks ago at the Buick Invitational, struggled to a round of 76 to finish well off the lead at even-par 216.
His round included a 10 on the par-3 fourth, his 13th hole of the day, when he hit four shots in the water. He responded by making three birdies over his final five holes.