Essex 136 for 5 (Zaidi 52, Dawson 3-24) beat Hampshire 135 for 8 (Napier 3-31) by five wickets
Ashar Zaidi's brutal hitting carried to give Essex their second NatWest T20 Blast win of the season and leapfrog Hampshire at the bottom of the southern division.
The Pakistan-born all-rounder came in at No 5, higher up the order than he has this season, to post a 32-ball 52, his highest T20 score for Essex. The consistent Zaidi has now scored 157 T20 runs this season in five innings.
He finally departed with six runs required when he was caught low down by Tino Best at mid-off after hitting four fours and two sixes.
But Ryan ten Doeschate saw Essex across the line for their first win at Chelmsford this summer with seven balls to spare.
Hampshire, who chose to bat, trundled along to what always looked a below-par 135 on a slow wicket, Graham Napier taking three for 31 and captain Ravi Bopara restricting the visitors to 15 runs off his three overs, for two wickets.
Bopara was later involved in a clear show of dissent when he questioned umpire Neil Bainton's decision to give him out lbw for nought. The incredulous Essex captain, already at the other end when the umpire's finger went up, implied that he had got bat on ball.
Essex's response was not without concern and they struggled against the spin of Liam Dawson, who took three for 24 in four tidy overs. But Zaidi and Tom Westley took the game by the scuff of the neck, adding 59 for the fourth wicket in 6.2 overs, and laying the foundation for a successful run chase.
Zaidi said of his promotion: "We decided that if the spinners were on, especially the leg spinner, it could be an option for me to go up the order a bit, particularly if it meant we could have a left and right combination. It worked well. It gives variety in T20 games and it can catch the opposition by surprise.
"I've been scoring some runs in T20, it was just a case of trying to get to fifty-plus and see the game out, which I nearly did. I'm not a stat man to be fair, but I am very happy with my form at the moment.
"There was massive pressure before the game because we haven't won many games. We have to win every game now, there is no other option."
Hampshire coach Dale Benkenstein said: "It is a very tough competition when you're lost a bit of confidence. The good thing for me is that we have almost got the future of the club playing now. Guys are going to start getting experience in the next few games."