Bottom-of-the-table Spalding came within one wicket of recording their second successive win, despite being bowled out for 129 at Louth.
In the closest game of the day, Warren Nel made 53 and shared a third-wicket stand of 63 with Jonathan Miles.
Miles then took the first five Louth wickets for 34 runs before Matt Hamilton and Graham West joined forces to add 58.
West also fell to Miles for 29 - giving the bowler figures of 6-20 - and the next two wickets fell for just seven runs, leaving Louth in trouble on 99-8.
The ninth fell on 107 but Andy Carrington and Tom Ryder dug in to take their side to the slenderest of victories.
On a day of low-scoring games, Sleaford managed 281-7n declared at home to Market Deeping - Andy Hibberd hitting 53 and Oliver Burford 60 - before bowling Deeping out for 168 to stay in sixth place.
Third-placed Bourne moved closer to Grantham but are still 24 points adrift after their win over Alford at Abbey Lawn.
Good bowling from the visitors saw wickets fall steadily and at 89-6, Bourne were looking at a low total.
But steady batting lower down the order from Jack Berry (31), Rob Bentley (35) and Tom Dixon (31) helped the home side to 201 before the final wicket fell.
Colin Cheer claimed the first three Alford wickets for 18 runs and, despite a spirited fightback from Nick Bennett with 52, the visitors were all out for 88 - Cheer finishing with 6-62.