The leaders are now 31 points ahead of their Trent Bridge rivals after declaring at 504 for six and then taking four wickets for 188, although they were held up late in the day by fifties from Alex Hales and Chris Read.
When bad light chalked off the last 10.2 overs - with the visitors still 316 behind - Hales had reached 80 not out and Read, ever the man for a crisis, was on 54 in a partnership worth 119.
Controversy erupted on the third day of the match between Somerset and Surrey at Taunton.
With the hosts on 191 for five in reply to 317, Murali Kartik ran out Alex Barrow as he was backing-up and Surrey skipper Gareth Batty declined the opportunity to call the 20-year-old batsman back when umpire Peter Hartley offered it.
While it was a legitimate dismissal, it is considered against the spirit of the game. Kartik and Batty were jeered by the crowd for the remainder of the innings, which saw Somerset bowled out for 294, Peter Trego making a defiant 92, including two sixes off Kartik and 13 fours.
By the close Surrey had reached 58 without loss in their second innings and led by 81 going into what now is sure to be a hugely competitive final day.
A composed innings of 70 by Keaton Jennings enabled Durham to have the best of the third day's play against Lancashire at Liverpool. Replying to the home side's first innings total of 262, Paul Collingwood's team were 187 for four at the close, still 75 runs in arrears but with only one day left to play in a match which looks set to end in a draw.
Half-centuries by Neil Dexter and Sam Robson helped lift Middlesex to 306 in reply to Worcestershire's 323 in the weather-hit match at New Road. Dexter led the way with 90 and figured in a century stand for the fourth wicket with Robson, who made 72.
By the close the hosts led by 61 on 44 for the losses of first innings century-maker Daryl Mitchell, Phil Hughes and Moeen Ali.
David Masters claimed another five-wicket haul before Derbyshire's lower order fought back strongly to leave the County Championship Division Two match against Essex at Derby fascinatingly poised.
The pace bowler finished with impressive figures of five for 51 from 30 overs but half-centuries from Ross Whiteley and Tom Poynton helped the Division Two leaders rally to reach 266.
Essex lost Jaik Mickleburgh in the fourth over of their second innings, but an attacking unbeaten half-century from Tom Westley carried the visitors to stumps on 85 for one, a lead of 64.
Yorkshire's promotion bid was again hit by rain as they suffered a washout for the second successive day against Gloucestershire at Scarborough.
Niall O'Brien struck a career-best 182 but Northamptonshire's clash against Glamorgan at Cardiff appears doomed to end in a tame draw.
Glamorgan had hoped to set up a winning position going into the final day but Northamptonshire seemed happy to settle for a share of the spoils.
Northamptonshire eventually declared their first inning 30 minutes before the end of the third day on 432 for eight. At the close Glamorgan had reached 10 for nought from seven overs.
Kent's bid for promotion looked in the balance with one day left of their crucial rain-hit game against Leicestershire at Grace Road.
After Kent declared at 350 for eight, the hosts reached stumps on 171 for three, only 30 runs short of avoiding the follow-on.
Fourth-placed Kent need a victory to keep their promotion hopes alive.