Champions-elect Deal suffered their first Premier Division defeat since October at Tunbridge Wells on Saturday.
Steve King’s side had won their last 11 league games while the 1-0 defeat was also the first time they’d failed to find the net since that last loss, 3-0 at home to Snodland on October 24.
Wells’ winner in front of a crowd of 422 at the Culverden was scored by in-form captain Trevor McCreadie.
The race for the play-offs looks set to go to the wire. Third-placed Corinthian made the trip to fourth-placed Faversham and it was Tommy Warrilow’s men who ran out 4-0 winners.
Nathan Wood gave Faversham an eighth-minute lead and captain Connor Essam quickly added a second. The points were made safe by a late brace from striker Stefan Payne, his second coming from the penalty spot.
To make matters worse, visiting defender Sam Fitzgerald was sent off in the second half after he got a yellow card.
Corinthian’s defeat means Deal need just four points from their last six games to win the title. Deal visit Lordswood on Tuesday night before hosting Lydd next weekend.
Erith Town made it three straight wins with a 2-1 success at home to VCD.
Harry Taylor had already hit the bar by the time James Miles gave them a first-half lead.
Taylor added a second after the break before VCD were awarded a penalty midway through the second half which was converted by Zak Bryon.
Whitstable enjoyed their biggest league win of the season, 5-0 at home to Sutton Athletic.
The hosts dominated the first half but didn’t go ahead until Emmanuel Oloyede scored on the stroke of half-time.
The goals flowed after the break with Will Thomas and Josh Oliver making it 3-0 within 10 minutes. George Sheminant added a fourth and James Jeffrey scored the fifth from the penalty spot late on after he was fouled in the box.
Bearsted are up to seventh following a 4-0 home win over Stansfeld with goals from Eniola Hassan, Ryan Blake, Robbie Roberts and Ollie Freeman.
Lydd lost ground despite coming from 4-0 down to draw 4-4 at home to Rusthall.
A remarkable game of two halves saw Rusthall head into the break with three points seemingly in the bag.
Jack Kirby and Jack Lyons both scored twice, the latter’s first goal coming from a stunning 30-yard free-kick.
But Lydd responded after the break with Charlie Dickens and Kenny Pogue quickly reducing the arrears.
Pogue made it 4-3 midway through the second half and Lydd twice hit the woodwork before levelling the scores in the last minute through Jamahl King.
Snodland can’t be ruled out just yet, they won 4-0 at Punjab United after scoring three late goals.
Francis Babalola scored after nine minutes but they had to wait until 20 minutes from time for Taylor Fisher to add a second. Fisher scored again before Alfie Eldridge netted in the 90th minute.
Lordswood came from behind to defeat Fisher 2-1 at Martyne Grove, Thomas Ngegba put Fisher ahead but Callum Peck equalised on 68 minutes and Matt Gething scored the winner with 10 minutes left.
A Joe Fisher penalty rescued a point for Kennington at home to bottom team Welling Town, who had led at one stage after falling behind to Adam Phillips’ 20th-minute opener for Ton.
The game of the day in Division 1 saw second host third as Rochester entertained Staplehurst.
There was only one goal in it with James West scoring the winner for Staplehurst from a free-kick after 35 minutes.