Although Somerset were relatively untroubled after being asked to survive a minimum of 62 overs across the final two sessions, Durham’s score of 400 for seven declared ensured they will have had a superior return in a game heading for a draw.
Durham began seven points behind their second-placed opponents but have enjoyed a five-point swing in Taunton.
After England paceman Steve Harmison dismissed former international team-mate Marcus Trescothick for the second time in the match with one that nipped away off the pitch, home captain Justin Langer hurtled to a 45-ball half-century.
Langer’s fifty included 10 fours and with support from James Hildreth, Somerset took tea at 111 for one, a deficit of just 65 runs.
Durham secured their fifth batting point – and halted immediately to deny Somerset an extra bowling point – when Callum Thorp clubbed leg-spinner Michael Munday for a straight six.
Contrasting half-centuries from captain Dale Benkenstein and Paul Wiseman ensured the full set after three morning wickets left the visitors 300 for six and requiring 100 runs in 24 overs.
Centurion Michael Di Venuto was one of the fallen trio, run out in the sixth full over of the day, having spent more than six-and-a-half hours compiling his 135.
Durham captain Benkenstein turned a delivery from Alfonso Thomas through the leg side and Di Venuto was short of his ground going for two when Munday relayed the ball to the bowler.
But at lunch Durham were within touching distance of their target, requiring 23 more from seven overs in the afternoon session.
Benkenstein struck a disciplined half-century from 96 deliveries while a higher-tempo contribution from Wiseman, whose own fifty took only 63, led to a declaration in the 128th over.
It was Wiseman’s positivity which boosted their chances, his counter-attack including six fours and a swept six off left-arm spinner Ian Blackwell.
Yet Somerset had begun with a spurt of successes, with Somerset seamer Thomas grateful to two good catches as left-handers Ben Harmison and Phil Mustard perished driving.
Ben Harmison was snapped up at short extra cover by a diving James Hildreth and Mustard followed when Langer pulled down a chance high to his right at mid-off.
The first hour of the fourth morning’s play in the top-of-the-table contest did not feature Marcus Trescothick, however, as the former England batsman was off the field nursing a migraine.
But he returned in the second hour and then opened up with Langer before perishing for his second failure of the contest, making only six.
Mark Stoneman (26)
Michael Di Venuto (23)
Will Smith (2)
Shivnarine Chanderpaul (3)
Dale Benkenstein (44) Captain
Phil Mustard (19) Wicket Keeper
Paul Wiseman (8)
Liam Plunkett (20)
Ben Harmison (14)
Stephen Harmison (10)
Mark Davies (4)
Callum Thorp (36)