|LV= County Championship Division One, Wantage Road|
|Close, day two: Sussex 368, Northants 251-7|
|Sussex 3 pts, Northants 2 pts|
Steve Magoffin starred with both bat and ball for Susses on a day when their slim hopes of finishing Division One runners-up were ended by Warwickshire.
Ashar Zaidi (88) and Magoffin (51) extended their overnight partnership to 113 before Olly Stone (5-48) wrapped up the Sussex innings on 368.
Magoffin (3-35) then dismissed both Northants openers to leave them 17-2.
Rob Keogh hit a first ton of the season (104 not out), supported by Ben Duckett (60), as the hosts replied on 251-7.
The morning session belonged to Australian fast bowler Magoffin, who hit his maiden first-class fifty for Sussex before his three scalps took him to 70 Championship wickets for the season.
There was controversy when James Middlebrook, playing his last game for Northants, was run out off the seventh ball of an over after an error by umpire Peter Willey.
Willey had initially called a no-ball when he adjudged Magoffin to have dislodged the bails in his delivery stride but, after consulting the fielders he called a dead ball.
The former Northamptonshire and Leicestershire all-rounder then wrongly allowed the seventh ball to be bowled, with which Zaidi ran out Middlebrook.
Keogh brought up his three figures and already-relegated Northants' 250 with two boundaries off the last over of the day.
BBC Sussex's Adrian Harms:
"Advantage Sussex at the end of day two largely due to Steve Magoffin and Ashar Zaidi.
"The wicket is slow and Sussex will have to work very hard over the next two days to claim a seventh win of the season and third place in the Championship."
BBC Radio Northampton's Chris Egerton:
"As well as Northants have battled here - and they have shown much more fight than they did seven days ago against Durham - Sussex have a significant advantage at half way.
"In a season in which he has suffered two broken fingers, Rob Keogh's unbeaten century is a testament to the hosts' spirit during this game."