A high-scoring game at Market Deeping saw more than 570 runs and two six-wicket hauls as Bracebridge Heath once again topped the 300 mark.
The visitors extended their lead by four points and now need just 26 from their final three games to win the championship for the third successive season.
They hit 318-8 with Matt Carter and Brett Houston making half-centuries and James Hook claiming six wickets for Deeping.
The home side were also on good batting form and a spirited chase saw them reach 254 before the final wicket fell.
Nick Green and Josh Smith shared an opening partnership of 116.
Green went on to add 114 to his ever-growing runs total while Brett Houston took six wickets for Bracebridge.
Bottom-of-the-table Spalding were all out for 109 but reduced Bourne to 7-2 then 69-6 before Sam Evison and Rob Bentley got together to deny their opponents any more wickets and take their side to victory.