Sussex slipped closer to defeat after being bowled out for 178 just before tea at Taunton on the third day of their County Championship clash.
It left Somerset requiring just 104 to win and complete an emphatic double over Sussex this season. With 39 overs left in the day there is a chance they could wrap it up with a day to spare.
After the top order was blown away by Alfonso Thomas in the morning it was always going to be a tall order for Sussex to turn the game around.
Ben Brown and Luke Wright briefly threatened to get the visitors back in the game as they put on 71 for the sixth wicket.
But when Brown was superbly caught by Alviro Petersen on 35 followed quickly by Wright and Luke Wells – batting with a runner - the chances of a sensational turnaround receded sharply.
Steffan Piolet and Will Beer frustrated Somerset by adding 56 for the ninth wicket before Piolet was caught by Marcus Trescothick at short leg off the bowling of George Dockerell having made 30.
Dockerell also removed Beer for 29 meaning Sussex’s lead was just 103. They will require some heroics from Magoffin to avoid only a second defeat of the season in division one.