Overnight leaders Dartford suffered a surprise 1-0 home defeat to struggling Poole Town, allowing Havant & Waterlooville to go top by a point after winning at Oxford City by the same scoreline.
Dartford put in a disappointing display at Princes Park to lose to third-bottom Poole.
What turned out to be the only goal of the game came after 63 minutes when Steve Devlin's free-kick was deflected in the penalty area and fell perfectly for Jamie Whisken to fire home.
Havant took over at the top, courtesy of victory at Oxford with a goal right on the half-time whistle from Jason Prior.
The Hawks now lead the Darts by a point and have two games in hand.
Third-placed Hampton & Richmond Borough are just a point behind Dartford now after beating play-off challengers Weston-super-Mare 3-1 at the Beveree.
The Beavers had to come back from a goal down when new loan signing, Mo Baghdadi, gave the Seagulls a 13th minute lead.
But goals from Bradley Hudson-Odoi after 35 minutes and Shaun Jeffers 6 minutes later took the hosts into the break in front.
And a second for Hudson-Odoi just past the hour-mark sealed the Beavers win.
Hemel Hempstead Town`s game was off, but none of the other top seven sides managed a win on Saturday, which was good news for both Welling United and Truro City, who both did so and closed the gap on the play-off places.
Chelmsford City were held to a 1-1 draw at fourth-bottom Hungerford Town, whose Nick Bignall looked to have earned his side all three points with his 35th minute goal leading going into stoppage time at the end of the game when Chris Dickson rescued a point for the Clarets.
Braintree Town were held to a 2-2 Cressing Road draw by a Wealdstone side who are twelfth but only five points behind the Iron now with two games in hand.
And they came back from two-down as Luke Allen and Billy Crook scored to give the Iron a 2-0 cushion in the 42nd and 45th minutes respectively.
Matty Whichelow reduced the deficit on the hour-mark and just 6 minutes later, Danny Green levelled.
St Albans City were the other top seven side to drop points – and it was a crucial three to Truro, who are just a point behind them now in ninth.
Connor Riley-Lowe`s 26th minute effort eventually proved enough for the White Tigers at Clarence Park.
Welling are also level on points with the Saints and the Iron after a goal from the returning Adam Coombes after 55 minutes sealed victory at East Thurrock United.
Bottom-markers Whitehawk`s run of one defeat in nine ended on Saturday as they were beaten 3-1 at the Enclosed Ground by fellow strugglers Chippenham Town, who are now four points ahead of the drop zone.
The Hawks, 14 points adrift of the safety mark, needed the points but conceded a 15th minute own goal, attributed to Kodi Lyons-Foster, and then a second to an Alex Ferguson effort 6 minutes into the second half.
It got worse for the Hawks when they had Kyjuon-Jaeger Marsh-Brown sent-off 19 minutes from time, although they did manage to reduce the deficit when Elliot Benyon scored from the penalty spot after he had been brought down.
But a third goal from Chippenham`s recent signing, Karnell Chambers, 4 minutes from time killed the game off.
Eastbourne Borough will need to look over their shoulders at the bottom end of the table after a 1-0 Priory Lane defeat by Gloucester City, courtesy of a 13th minute Joe Parker effort, leaves Boro only six points above the drop zone.