Essex 33 for 5 trail Hampshire 254 (Bailey 89, Vince 60, Porter 4-53, Harmer 3-47) by 221 runs
Hampshire new-ball partners Kyle Abbott and Fidel Edwards gave Essex a champion's hangover - as the Specsavers County Championship Division One winners suffered a batting collapse at the Ageas Bowl.
Former Test fast bowlers Abbott and Edwards shared four wickets for 23 to leave Essex on 33 for five overnight after Hampshire had posted 254 thanks to classy fifties from James Vince and George Bailey.
Essex were confirmed as 2017's title holders last week having thrashed Warwickshire but stumbled on the south coast. However, they will be keenly aware that, with relegation positions so tight, they need to compete until the end out of courtesy to the other sides at the bottom end of the table.
Their reply started terribly as Nick Browne failed to pick up the pace of Abbott to fall in the second over.
Varun Chopra was bowled by the South African four overs latter to give the fast seamer his 50th first-class wicket of the season.
Abbott's opening partner Edwards joined the party in the following over to have Tom Westley lbw, as the visitors slumped to 12 for three.
Dan Lawrence and Ravi Bopara steadied the ship by blocking out eight overs, before the latter was bowled by Gareth Berg without playing a shot.
Essex sent out nightwatchman Sam Cook to see out the remaining six overs but he only managed two before he was bowled by Edwards - leaving his side 221 behind.
Earlier, Essex's wicket-taking duo Jamie Porter and Simon Harmer took their combined tally for the season up to 134 scalps, after captain Ryan ten Doeschate bowled without a toss on a good bowling track at the Ageas Bowl.
The pair's wicket-taking ability has been one of the main reasons behind Essex's Division One triumph.
But it was Porter's new-ball partner Cook who made the first blow into Hampshire's batting line -up as he struck Jimmy Adams in front in the second over.
Porter wasn't to be overshadowed for long as he had Joe Weatherley lbw to leave Hampshire struggling on 14 for two.
Vince and Tom Alsop came to the host's rescue with a punchy counterattacking stand worth 71 runs.
The partnership ended when Alsop shouldered his arms at a straight delivery from Porter, with Vince completing his 30th first-class fifty in 65 balls soon after.
But Vince departed soon after lunch when he feathered a back-foot drive behind off Cook.
Spinner Harmer then took centre stage to claim his 64th, 65th and 66th wickets of the campaign.
The South African off-spinner had Sean Ervine caught well by an off-balance Chopra at first slip and Ian Holland bowled, either side of Porter bowling a slow-scoring Liam Dawson.
Harmer added Berg to his long list of victims as the Hampshire all-rounder edged behind.
While the wickets were falling at one end, captain Bailey was accumulating runs at the other in fluent chanceless style.
The Australian reached his half-century in 79 balls but slowed up as the softer ball made rapid scoring more difficult.
Hampshire reached a second batting point, which could be important in an unlikely relegation battle, as Abbott was caught at first slip.
Bailey, on 89, decided he need to farm the strike and score boundaries, with unreliable Edwards occupying the other end, but holed out on the mid-wicket boundary attempting a maximum to leave his side all out for 254.