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Maidstone need four points from two games to win the Ryman League Premier Division after beating Grays on Saturday.
United's 2-1 victory coupled with Hendon's 2-2 draw at Dulwich Hamlet has moved Jay Saunders' side six points clear. Hendon still have a game in hand but it's United's title to lose.
All the goals came in the second half with Frannie Collin scoring the winner after Jay May's opener was cancelled out by Jamie Stevens.
Maidstone reverted to the diamond system that worked so well against Margate but Grays looked dangerous on the break and went close several times in the first half without forcing a save from Lee Worgan.
Stones worked away keeper Lemar Johnson through Jack Parkinson's awkward 25-yarder and an Alex Brown strike before Billy Bricknell lashed just wide after a neat move involving May and Collin.
May saw a header well held near the end of the half but United could probably count themselves lucky to be level.
Stones introduced Matt Bodkin for Bricknell at half-time in a change of shape to 4-4-2.
And they led on 51 minutes with Collin's corner turned home by May in the six-yard box.
Brown dragged wide when through from May's pass after Collin forced a mistake from Sean Cronin.
But Grays levelled soon after through Stevens' deflected free-kick on 68 minutes after a foul by Steve Watt.
Bodkin had an effort blocked from the restart then it was his cross that gave May a free header at the far post that went straight into the keeper's arms.
Grays went close again before Stones regained the lead, Collin picking up possession and finding the bottom corner from 20 yards with an excellent strike.
Collin's header from a Ben Greenhalgh cross was well tipped over as Stones looked for a third.
Maidstone: Worgan, Stone, Mills, Watt, Miles, Rogers, Brown (Greenhalgh 77mins), Parkinson, May, Collin, Bricknell (Bodkin 46mins). Subs not used: Miles, Paxman, Godmon. Attendance: 2,094.