Surrey 47 for 2 (Sudharsan 20*, Patel 14*, Abbas 2-20) trail Hampshire 219 (Brown 78, Lawes 5-27) by 172 runs
Tom Lawes took back-to-back five-wicket hauls as Surrey claimed three of the five points needed to be crowned LV= Insurance County Championship winners.
Allrounder Lawes pulled out the Hampshire middle order for his third five-for of the season with Kemar Roach picking up 3 for 41.
Hampshire built their below-par 219 around Ben Brown's positive 78, before Mohammad Abbas pinned back Surrey to end the day on 47 for two - a deficit of 172.
Surrey needed five points to be confirmed Champions for a second year in a row - even if they failed to do so all they'd need to do is avoid defeat to prevent Essex from overtaking them.
Early morning rain saw the toss, and play, delayed by an hour before Surrey choose to bowl - with Jamie Smith and Will Jacks likely to boost the batting once they return from England duty.
It took until the ninth over for Surrey to open up the Hampshire top order as Toby Albert jabbed unconvincingly at Roach to edge to second slip Jamie Overton. In the West Indian's following over, he found Nick Gubbins chopping on a floaty ball outside off stump.
Point one of five was chalked off in the 18th over when James Vince's back-foot swish was gobbled by Overton to hand Lawes his first wicket with his fourth ball.
The pitch didn't appear to have any demons but Hampshire's batters struggled to escape the accurate Surrey bowler's clasp. Fletcha Middleton was a fine example of this as he battled hard for 52 balls before losing patience against Jordan Clark - who cleaned out his off stump.
Lawes had been forced to wait until senior bowlers Roach, Dan Worrall, Jordan Clark and Overton had their go, but the 20-year-old out-shone them all. The pace bowler claimed 5 for 105 against Northamptonshire last week and slaughtered the Hampshire middle-order.
After Vince, Tom Prest was Lawes' next victim when last week's century-maker followed his captain in wafting on the back foot - this time Ben Foakes grabbed the simple catch.
The match-winner in Hampshire's sensational victory over Essex last week, which put the title in Surrey's hands, Liam Dawson failed to replicate his heroics as he drove to second slip.
Ian Holland stuck around to put on 33 with Brown - who was starting to get into his work - before Roach returned to strangle him down the leg side.
Brown was forced to guide the tail through things to get the score towards respectability, with stands of 55 and 45 with James Fuller and Kyle Abbott.
The wicketkeeper has had a disappointing season with the bat in the Championship, with this his third fifty of the campaign. His best being the 95 he scored in the reverse fixture at the Kia Oval in April. His ten boundaries all came square or behind the wicket on his way to a 63-ball half-century.
Fuller fell after a nicely crafted 25 when he was lbw to spinner Cam Steel before Brown gave a fourth wicket to Lawes and a fourth catch to second slip Overton, a third point in the bag for the Brown Caps.
Abbas was the last to fall for a four-ball duck when Lawes pinned him leg before.
Surrey had 20 overs to bat under the now clear skies with 300 in their sights to win the title. Abbas had other ideas as Dom Sibley faintly edged behind and Rory Burns played onto his stumps for evening figures of 2 for 20. But Ryan Patel and Sai Sudharsan carefully guided the visitors to the close.
