Senior, who posted the lone score under par in the third round, stands at 4-under-par 212, alongside Bill Lunde, who shot 1-over 73.
Doug Barron and last week's winner Euan Walters both posted rounds of even-par 72. They share third place with Scott Sterling (74) at 3-under-par 213.
Former PGA Tour winner Franklin Langham and Gavin Coles, the 2002 Jacob's Creek Open Championship winner, are one stroke further back at minus-2. They are joined there by Steven Alker, Bradley Hughes and Brendan Jones.
Senior began his day six shots behind overnight leader David Diaz. Senior opened quickly with a birdie at the first. After a series of pars, he converted another birdie try at the par-four eighth.
The 44-year-old fell back to minus-2 as he bogeyed the par-3 11th. He fought back to birdie the 15th.
Senior capped his round with a birdie at the par-4 closing hole at the Clearwater Resort to move to 4 under.
'I just tried to make no mistakes, especially on the easy holes,' said Senior. 'I made a birdie on eight which was like picking up two on this course. I've been hitting a lot of good iron shots and driving the ball pretty well this week. Tee to green's been good and I made a couple of good putts today.'
Lunde birdied the fourth, but stumbled to a bogey at the very next hole. However, he stood at minus-5 and owned a piece of the lead when Jon Mills bogeyed the sixth.
Lunde made another bogey at the 10th, but responded to reclaim a share of the lead at 5 under with a birdie on No. 11. He faltered to a late bogey on the 17th to drop back into a share of the overnight lead with Senior.
Senior, who was in one of the early groups to tee off, stood three shots behind the leaders when he finished.
Lucas Parsons tied Diaz for the lead at one point at minus-7. Parsons fell out of the lead with a triple-bogey at the fifth. He stumbled to another triple-bogey and also had a double-bogey en route to a 7-over 79 to fall to 2-over-par 218 for the tournament.
Diaz did not fair much better. He dropped out of the lead with a double-bogey at the fifth. Diaz carded three more bogeys and a double-bogey on his way to a 6-over 78. He stands at 1-under-par 215.
He is joined at minus-1 by Shane Bertsch (73), Richard Best (75) and Paul Sheehan (73). These four are the final of just 14 players under par, the result of nearly 50 m.p.h. winds and driving rain.