Wellington are one point behind after eking out a four-wicket win over Central Districts.
A powerful CD batting lineup could only manage 212-9 at McLean Park, with powerful 19-year old Josh Clarkson continuing his strong start to the campaign by top scoring with 68.
Anurag Verma took 5-44 for Wellington, and his side's economical bowling unit seemed to have made things easy for the batsmen.
A 55-ball 50 from Michael Papps and 40 from English import Scott Borthwick had them well on track, but two Blair Tickner wickets and economical spin bowling led by George Worker (3-35) gave the contest some intrigue.
For the second time in four days, Luke Woodcock came to the rescue, starting slowly but safely as he eventually dragged Wellington above an always-accessible run rate.
The veteran all-rounder finished unbeaten on 63, and Verma chipped in with the bat to guide the Twenty 20 champions home with eight balls to spare.
Northern Districts occupy third spot after crushing Canterbury by nine wickets. 21 year old debutant Brett Randell proved it was a day for the youngsters, claiming 4-38 as Northern routed Canterbury for just 137.
Scott Kuggeleijn (2-36) and Brett Hampton (3-24) also contributed as Canterbury collapsed from 80-2, with only 20 year old Jack Boyle providing any resistance with 40.
ND made quick work of the chase, with openers Joe Carter (64) and Dean Brownlie (55 not out) sealing a bonus point victory.