Middlesex 84 for 3 trail Hampshire 336 (Dawson 89, Murtagh 3-64) by 252 runs
Middlesex batsman Dawid Malan staged a batting comeback after the visiting county lost early wickets - to leave their Specsavers County Championship game with Hampshire in the balance.
Malan reached 40 before the clouds breezed in to force the players off for bad light at 2.50pm before rain curtailed day two early with only 41 overs bowled.
Malan was given a lifeline on 26 when he edged to Will Smith at gully, only for the usually reliable former Durham captain to fumble to chance, which had come at him at a fair speed.
He bashed six boundaries during his relatively quick innings - after Hampshire had struck early following being bowled out within the first hour.
Sam Robson started the season with a double century/century, combination to kick-start his hopes of playing for opening alongside Alastair Cook this summer.
But he only reached 5 before he slapped a thickly edged cover drive to Michael Carberry standing at point off James Tomlinson - the left-arm seamer's ninth wicket of the year.
Nick Compton, who currently holds a position in the England Test side, has endured getting in and getting out so far in 2016, but on this occasion he only managed the latter.
Hampshire's pace attack had put Compton under huge pressure with accurate bowling before Ryan McLaren forced him to push outside his off stump - Jimmy Adams completing the wicket at first slip.
Nick Gubbins stuck around slightly longer than his partners, as he forged a 33-run stand with Malan, before following a leg-side delivery on his hips through to Adam Wheater, to give McLaren his second.
Middlesex were three-down on the scorecard but in effect four-down with Adam Voges playing no further part in the match following his head injury on day one - although he was on the ground to watch his team-mates.
Hampshire director of cricket Giles White and Middlesex head coach Richard Scott had a discussion whether to allow a replacement but could not find a way without falling foul of the laws.
Malan and wicket-keeper John Simpson saw Middlesex to the premature close - trailing Hampshire by 252 runs. Earlier, the visitors needed exactly seven overs to bowl Hampshire out for 336.
Liam Dawson had looked set for three figures after a patient 86 on the first day, but could only add three morning runs before he edged Steven Finn behind to Simpson.
West Indian Tino Best livened the session up with some Caribbean flair, as he attempted to knock the leather off the cherry - and almost succeeded with a colossal six come down the track to the pacy James Harris.
Tailenders Mason Crane and Tomlinson both fell for ducks to end the innings - Tim Murtagh his third of the innings and Finn his second.