Hampshire 148 (Northeast 53, J Overton 3-22, J Davey 3-40) and 75 for 4 (C Overton 3-16) beat Somerset 106 (Abbott 5-31) and 116 (Trescothick 50, Steyn 4-34, Abbott 6-40) by six wickets
Somerset slid to a two-day defeat at the Ageas Bowl to give Surrey the chance to seal a first Championship title since 2002 by avoiding defeat at New Road.
Hampshire's new-ball pairing of Kyle Abbott and Dale Steyn took all ten wickets as Somerset were bowled out for just 116 in their second innings, and despite a momentary scare when they were reduced to 21 for 3 chasing 75, Jimmy Adams' unbeaten 25 took them over the line before five sessions had elapsed.
Questions will be asked of a pitch that gave plenty of assistance to the seamers throughout, but there would be a certain irony if Somerset, whose Taunton pitch has been scrutinised more than once in recent years, were to complain about excessive movement.
Conditions were gloomy enough that the floodlights were rarely turned off, and batsmen on both sides will look back at certain shots with little fondness. While it is easy to view those shots in isolation, minds are scrambled when there is noticeable movement off the seam and the bounce is variable.
Somerset captain Tom Abell had few complaints about the pitch, and ultimately it will be the opinion of Cricket Liaison Officer Wayne Noon that matters. There is some chance this pitch will be deemed to be 'below average', but that eventuality would not mean a points deduction for Hampshire, as it would be their first such wicket in the past 12 months.
While Somerset will be disappointed to have folded for less than 200 for the fourth innings in a row, their second-innings total of 116 was that low primarily on account of high-quality seam bowling.
Abbott, who now has 30 wickets in Hampshire's past four matches - of which they have won three - was exceptional throughout the two days. Abbott said that he had "lost a little bit of self-belief" in the first part of the season, when he bowled without rhythm or confidence in his action, but here he looked every bit the South Africa international that Hampshire were so chuffed to have signed last spring.
As Marcus Trescothick stood firm, Abbott made early inroads to leave Somerset 20 for 4 and still behind the game. He cleaned up Ben Green and Tom Abell with two late inswingers, and also accounted for Azhar Ali and James Hildreth in a matchwinning opening spell. He ended with 6-40 to secure a fourth five-wicket haul in five innings.
At this stage of the season it is easy to reduce Championship cricket to a series of permutations and hypotheticals about how different results will affect title charges and relegation battles. But it was impossible to ignore the subplot played out between Steyn and Trescothick.
The pair have less history than one might think - they played against one another just three times at international level - but when Trescothick became Steyn's first Test victim in 2004, with an inswinging 87mph yorker that clattered into middle, the prospect of them fighting it out in the County Championship 14 years later must have seemed a little fanciful.
Instead, it was a gripping contest. Steyn spent most of his opening burst probing around off stump as Trescothick played inside the line of the ball time after time, and while all hell broke loose at the other end, he remained resolute.
With the lead just 40 and Somerset eight down, Steyn then hit Trescothick on the head with a vicious short ball. After giving himself an over to settle down, Trescothick clipped Steyn for four and then pulled him for six - a shot which took him past 26,000 first-class runs - and after repeating the trick to go to a valiant 50, he played on two balls later. Trescothick had won the battle, but Steyn the war.
Steyn ended with four wickets, and bowled as well as he has done since joining Hampshire as overseas player. While Morne Morkel's move to Surrey remains the indisputable impact signing of the summer, the combination of the fit-again Steyn and a resurgent Abbott - who, to channel Arsène Wenger, has been like a new signing - has helped Hampshire effectively seal their Division One status with games against strugglers Yorkshire and Lancashire to come.
"I haven't really seen a pitch play like that here," Abbott said. "It is unusual because it doesn't look too different to the pitches we have played on here. The wickets are playing very strangely at this time of the year which is good for me but not good for the top order batsmen."
In truth, Hampshire always looked likely to reach their target of 75, and in spite Craig Overton's three-wicket burst, they had the perfect man for the situation in Adams.
His stand of 25 with Sam Northeast - who has contributed plenty to the last two wins - acted as a sedative to the jangling nerves of the home supporters, and Tom Alsop's late flurry took them over the line.
Somerset now face the challenge of putting the disappointment of the past ten days behind them in time for Finals Day on Saturday. They are helped by the fact there is substantial changeover between their Championship and Blast sides, but disappointment at Edgbaston would mean these past few weeks have a distinctly familiar feel for county cricket's perennial bridesmaids.