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Second-half goals from Andy Drury and stand-in captain Dave Winfield ensured Ebbsfleet took the National League South title race to the final day of the season.
Leaders Maidenhead needed only a point to win the title and they looked on course at half-time courtesy of Dean Inman's opener.
But Fleet had other ideas and Maidenhead had to put the champagne on ice after falling to their first home defeat of the season.
Maidenhead will still claim the title with a final-day win at Margate while Fleet host Oxford City but at least Daryl McMahon's men avoided having to see the trophy presented before their own eyes.
Fleet made three changes. Bradley Bubb, who was ruled out with a long-term Achilles injury picked up in training on Thursday, was replaced by Dean Rance, while Anthony Cook was in for Sean Shields and Aaron McLean played up front instead of Darren McQueen.
Although Jack Powell shot wide early on for Fleet, Maidenhead had the best of the early play. The hosts went close on 14 minutes when Fleet keeper Nathan Ashmore failed to gather a deep corner and Sean Marks' header hit the bar before being cleared to safety.
Fleet hit the woodwork themselves four minutes later when Cook skipped past on-loan Dover midfielder Jack Parkinson but his 25-yard shot hit the top of the bar.
Maidenhead's leading marksman Dave Tarpey curled a left-foot shot at Ashmore from distance before the hosts went ahead on 21 minutes. A short corner saw a far-post cross headed in by defender Inman.
Fleet, playing a 4-5-1 formation, never really got their passing going with too many balls failing to find their intented target in the opening 45 minutes. When they did get it right, they nearly produced an equaliser seven minutes before half-time.
Powell and McLean combined to set up Sam Deering, whose pull back for Drury saw the Fleet midfielder let fly from 20 yards but his shot clipped the outside of the post.
Powell had two free-kicks that failed to find the target early in the second half before Fleet introduced McQueen and reverted to 4-4-2 on the hour.
Ashmore produced a stunning one-handed save to deny Tarpey after a neat exchanges with Marks on 63 minutes and it proved a pivotal moment as Fleet were back on level terms just two minutes later.
Deering had time and space on the edge of the box and picked out Drury, whose left-foot shot was out of the reach of home keeper Carl Pentney.
Fleet were passing the ball much better, with their confidence up and Drury and Deering both influential figures.
They went ahead on 74 minutes when Pentney flapped at a right-wing corner and Winfield hooked the ball home at the far post. That put the title celebrations on hold for the home side, who then seemed to lose their way.
Referee Sam Purkiss played more than eight minutes of additional time as the game became stop-start late on but the Fleet held on to the three points. Ashmore appeared to have objects thrown at him by the home fans late on and the referee struggled to keep a lid on proceedings before finally bringing the game to a close.
Maidenhead: Pentney, Clerima, Steer, Parkinson (Upward 74mins), Massey, Inman, Tarpey, Comley, Marks (Cox 66mins), Mulley (Smith 78mins), Pritchard. Subs not used: Wiltshire, Peters.
Ebbsfleet: Ashmore, Cook, Connors, McCoy, Winfield, Clark, Powell, Drury, McLean (Shields 85mins), Rance (McQueen 60mins), Deering (Mambo 90mins). Subs not used: Phillips, Jordan.
Attendance: 3,377.