Centuries from Sam Northeast and Ian Holland have put Hampshire in a strong position to wrap up victory on Sunday against Middlesex at the Ageas Bowl.
Northeast and Holland added 257 for the third wicket before James Vince declared half-an-hour before lunch - setting Middlesex an unlikely target of 531 for victory.
The signs looked ominous for a three-day finish when the visitors were reduced to 33/3 - having been dismissed for 76 in their first innings on Friday.
However, a stand of 122 from Nick Gubbins and Robbie White for the fourth wicket gave Middlesex their first partnership of note for the match to frustrate the home side.
It was part-time seam bowling of Holland that finally made the breakthrough when he enticed Gubbins with a wide delivery during the extended final session and Liam Dawson took a sharp catch to dismiss the left-hander for 67.
But White, 73, and Martin Andersson, 25, took their side safely to the close with the new ball due in 11 overs.
Northeast, who was on 99 overnight, reached three figures in the third over of the day with a sweetly-timed cut shot to the boundary, to follow up on the classy 63 he made in testing conditions on day one.
Opener Holland then became the fifth batsman in Hampshire's top-six to reach three figures in the opening two matches of the season before Steve Finn ended the partnership when he bowled Northeast for 118.
Vince also fell to Finn for a duck when he was adjudged to be lbw to a ball from the former England paceman that looked to be drifting down the leg-side.
The Hampshire skipper then called in the unbeaten Holland, after he had reached his highest first-class score of 146 and new batsman Dawson.
Middlesex made it unscathed to the lunch interval, but lost 3-7 immediately after the restart when Mohammad Abbas bowled Sam Robson for 19.
Kyle Abbott then trapped Max Holden in front of the stumps for 10 before Abass took his eighth wicket of the match when Steven Eskinazi edged to Joe Weatherley at slip for a single.
Batsman Nick Gubbins said: "It was a really pleasing day for the team. After yesterday everyone was bitterly disappointed. The players, the coaches, we were all very disappointed with the way we performed and it was great that we managed to stand up and do much better today.
"It was incredibly frustrating for me to get out when I did, but really great to see Robbie (White) and Martin Andersson continue to bat until the end of the day."
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