The Spireites were the better side for much of the first half and the early part of the second, before their visitors slowly but surely wrestled control of proceedings.
Sloppy defending aided the Spitfires when it came to their goals, but the mistakes were a result of pressure created by the away side.
It was a game Town never should have lost, however, having gone ahead first through Haydn Hollis and then through Scott Boden.
The visitors were on the attack inside the opening minute, Chris Zebrowski latching onto a loose ball on the left and curling a shot past Shwan Jalal’s far post.
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It was an open start to the game, Scott Boden threatening to break free of the centre-halves and going down under their challenge, referee David Richardson unimpressed.
Charlie Carter went on a dribble through the middle of the pitch and found Boden on the right side of the area, but the striker horribly sliced his cross.
The hosts seemed to settle into their rhythm, Robbie Weir snuffing out attacks and trying to get his side going forward, Tom Denton winning his headers - one of which fell wide of goal from an Ellis Chapman free-kick.
Chesterfield were reminded of their visitors’ threat when a ball forward allowed Zebrowski to get the wrong side of Haydn Hollis, keeper Shwan Jalal rushing out to challenge and pressuring the forward into poking wide.
But Town deservedly took the lead on 33 minutes, Denton winning a free-kick that Chapman clipped into a dangerous area, Will Evans heading across goal for Hollis to tap home from a yard out.
With their tails up, the Spireites went hunting a second. Evans got the home fans on their feet with a storming run from deep in his own half to 30 yards from the Eastleigh goal, drawing Andrew Boyce into a foul that saw him yellow carded.
Having struggled to break the hosts down, Eastleigh finally got a little slice of luck and took full advantage to level the game.
Town seemed in control near their own corner flag until a bounce of the ball gave Zebrowski a sniff and he latched onto it, sending a cross to the back post for Paul McCallum to rise above Josef Yarney and head in the equaliser.
Parity didn’t last long, however.
The second half was just four minutes old when Chapman nipped in to pick the pocket of a defender before playing a lovely early ball across goal, Boden arriving at the back post to sidefoot Town in front again.
Chesterfield looked quite comfortable and had good spells of possession, but once again all Eastleigh needed was a half chance and they were clinical.
The home side lost Joe Jones at a corner, his free header at the back post drew a crowd and with Jalal out to challenge for the high ball, Andrew Boyce nodded into the unguarded net.
Eastleigh began to take control of the game, enjoying more possession and territory, forcing the Spireites to sit deeper and deeper.
It wasn’t long before a chance came the way of Ben Strevens’ men, a Yeates cross flashing through the goalmouth, McCallum straining unsuccessfully to get a touch.
Although fresh legs in the form of a Chesterfield double change stemmed the tide, the visitors were able to soak up a little pressure and counter perfectly to take the lead for the first time.
Jones strode right down the middle of the pitch and with blue shirts backing off, unleashed a wonderful strike that gave Jalal no chance.
Chesterfield huffed and puffed a little before the final whistle but created little, Eastleigh seeing out five minutes of time added on to celebrate an important three points in their promotion bid.
Chesterfield: Jalal 6, Smith 5, Chapman 6, Hollis 6, Evans 6, Yarney 5, Weir 7 (Shaw 73), Weston 5, Carter 6(Binnom-Williams 73), Boden 7 (Fortune 79), Denton 7. Not used: Maguire, Anyon.
Eastleigh: Southwood 6, Hare 6, Miley 6, Boyce 6, Wynter 6, Jones 7, Holland 5, Gobern 5, Yeates 6 (Hobson 90), McCallum 7 (McKnight 82), Zebroski 7 (Williamson 70). Not used: Green, Dennett.
Goalscorers: Hollis 32, Boden 49; McCallum 44, Boyce 60, Jones 83
Yellows: Gobern 21, Boyce 36, Hollands 52
Referee: David Richardson. Assistants: David Pill, Paul Tomes.
Attendance: 4,319 (100 away)