Hampshire 196 (Dawson 103, Gregory 3-63) and 176 for 8 (Vince 102*) lead Somerset 142 (Abbott 9-40) by 230 runs
A relentless Kyle Abbott ran through Somerset's batting line-up to finish with the best figures in the County Championship since in three years and dent their hopes of winning a maiden title.
Abbott's overnight figures had been impressive - he had two wickets for one run in six overs - and he added a further seven on a bright, sunny day, moving the ball prodigiously off the seam while hammering away at a good length.
Despite some resistance in the form of a dogged 67-run stand for the ninth wicket between Dom Bess and Roelof van der Merwe, Somerset folded for 142, leaving them 54 runs in arrears.
They struck early with the new ball, leaving Hampshire in trouble at 45 for 6, before James Vince's sublime, unbeaten 102 wrestled control back, while events at Chelmsford confirmed that next week's game at Taunton will be a title decider regardless of what happens in this round of games.
The reasons players sign Kolpak deals are myriad and complex, and Abbott has no regrets about his decision to do so back in 2017, but it was impossible to watch this display without a tinge of sadness that he has played his last game of international cricket.
Many of his best balls did not take wickets, and instead jagged away late off the seam past the outside edge; but the balls to remove Tom Abell (bowled shouldering arms), James Hildreth (feathering behind) and George Bartlett (trapped lbw in front of off stump) all stuck in the memory as deliveries about which little could have been done.
The wicket here has been an unusual one. In each of the three innings thus far, it has looked like a snakepit when the seamers are armed with a new, hard ball; once it has softened, the dryness underneath the grassy top has made the surface comparatively placid. Somerset picked two spinners in the expectation that it might turn as the game wore on, but movement off the seam, coupled with good pace and slightly irregular bounce, has been the key factor in keeping the scores down.
Vince signalled in the aftermath of the game against Surrey last week that his side were "motivated to turn in a strong performance" to spoil Somerset's party, and he appeared to have taken that mantra to heart in his innings.
He took 23 balls to get off the mark, and was unbeaten on five after 43, before flying through the gears faster than a sixth-former in the outside lane in their first time on the motorway, creaming 14 fours as he reached a sublime hundred from 136. The pick of them were an outrageous one-two off Abell's medium pace; the first a length ball whipped from outside off stump through midwicket, the second a late cut dabbed through third man for four.
Within five overs of being joined by Abbott, batting at No. 10, Vince was faced with a field comprising a wide slip, and eight men on the boundary. It did little to deter him, and he manoeuvred the strike expertly in their unbeaten partnership, which stands at 73 overnight.
"Wishing all the luck in the world to Somerset today! This could be our first County Championship in 600 years," John Cleese had tweeted on Monday morning, and the club's wait has been so long and agonising for their supporters that it might well feel as though he wasn't too far out in his exaggerated calculations.
In the film Clockwise, Cleese's character Brian Stimpson cries: "It's not the despair, Laura. I can take the despair. It's the hope I can't stand." So it must feel in Taunton on days like this.
There have been points at which Somerset have seemed in control of this game, but they now find themselves needing to make the highest total of the match in the fourth innings if they are to win.
But today's struggle with the bat effectively confirmed what was already apparent for Somerset: if they do win the title, it will likely be in spite of, rather than because of, their batting. No player averages more than 35 this season, while nobody is near the aggregate of 1000 runs that was once used as a benchmark.
There are extenuating circumstances - only one ground, Chelmsford, has seen fewer runs scored per wicket than Taunton's 23.95 - but the reality is that few teams win pennants without a single batsman having a notable season.
Jason Kerr, the head coach, is not waiving the white flag just yet. ""I think the surface is changing," he said, "and if we can get through with the new ball then I think we are in the game. Hampshire scored 400 in the third innings last week and it is a similar pitch to this. There is a great opportunity for us tomorrow."
It is fighting talk, but with Abbott in this form, getting through the new ball is hardly a simple task. And with the forecast for next week's game looking decidedly iffy, it is clear that tomorrow's events will go a long way towards determining the identity of this year's champions.