Michael Yardy and Matt Machan's efforts with the bat were followed by a stunning spell of bowling from James Anyon to put Sussex on course for a heavy victory over Somerset after day two at Taunton.
Yardy struck the six runs needed to move to three figures on the second morning and went on to post 156 as Sussex were all out for 363 - a first-innings lead of 119.
Somerset closed on 197-7 in their second innings, a lead of just 78 with three wickets in hand.
Machan was also a heavy contributor to Sussex's tally and his innings of 103, his maiden first-class century, came during a partnership of 275 for the third wicket with Yardy.
Seam bowler Craig Meschede (2-56) removed Machan before lunch and, from 283-2, Sussex lost 8-80 with all six bowlers tried by Somerset skipper Marcus Trescothick picking up at least one wicket.
But Trescothick then completed a pair - and his fourth straight duck in all competitions - when Anyon had him caught behind in his opening over for the second time in as many days.
Sense of humour
Walking back to the pavilion he took off his helmet and raised his bat to the crowd, suggesting his sense of humour remains intact.
Nick Compton, discarded by England for the Ashes opener, was bowled by Magoffin for seven to also complete a miserable match and leave Somerset on 31-2.
James Hildreth hit seven fours in his 49 but wickets continued to go down regularly as Anyon and Magoffin steadily worked their way through the middle order.
Jos Buttler (35) and Craig Kieswetter (37) shared a 66-run stand for the sixth wicket but fell in successive overs late on to complete Sussex's excellent day.
Anyon took 4-56 to hit Somerset's prospects, while Steve Magoffin picked up two scalps to give Sussex, who would move above current table-toppers Yorkshire with victory, total control.