Northants need to reach 197 to beat Leicestershire and remain in with a chance of securing promotion on the final day of the Specsavers County Championship Division Two season.
David Ripley's men bowled Leicestershire out for 270 in the second innings, with Simon Kerrigan taking four for 62 and Ben Sanderson three for 60.
That meant the home side held a 196-run lead at Grace Road, but Northants chipped away at that before the close, finishing the third day on 17 without loss.
They now need to finish the job on Thursday and hope that Nottinghamshire suffer an unlikely defeat at Sussex.
Notts have a first innings deficit of 88 runs, but Sussex would have to score quickly and then bowl Notts out cheaply to earn the win Northants need for promotion.
At Grace Road, Northants, shorn of leading wicket-taker Rory Kleinveldt through an injury picked up the previous day, looked to be struggling with the Foxes on 228 for five at tea.
Mark Cosgrove appeared to be taking the game away from the visitors in racing to 80, but seamer Sanderson won a leg before decision against the Leicestershire skipper.
All-rounder Ben Raine then hooked a bouncer from the same bowler straight to deep square leg to open an end.
On-loan left-arm spinner Kerrigan had Zak Chappell stumped as he dragged his back foot attempting a straight hit.
Richard Gleeson then trapped a disbelieving Lewis Hill leg before and Kerrigan bowled Dieter Klein to leave Northants, who had made 202 all out in their first innings, with a target of 197.
Luke Procter and Rob Newton reduced that by 17 before bad light and rain ended play 16 overs early.