With seven overs left, ND needed 52 with six down. A late stumble threatened to undo ND's defiance and when debutant spinner Vishi Jeet, who had Brownlie out earlier in the day, dismissed Watling in the penultimate over, Aldridge and Baker -- who had a good game with a 10-wicket haul -- were left to hang on.
Canterbury went four points clear with a nine-wicket win over Wellington yesterday.
Chasing 172 they got there for the loss of only Ronnie Hira for 71.
Opener Greg Dawson, with 50, and Neil Broom, who was on 43 at the finish, carried Canterbury to the win.
Central Districts' visit to Queenstown ended as it began, rain ruining the final day of a drawn match.
In the fifth round of games, CD host ND in New Plymouth and Wellington play Otago in the capital on Sunday, while Canterbury meet Auckland in Rangiora starting on Monday.