Australia opening batsman Chris Rogers hit a fluent 67 not out to lead a Middlesex fightback to 96 for no wicket after Nottinghamshire declared at 430 for seven in their LV= County Championship Division One match at Lord's.
Andre Adams had bludgeoned five sixes in a 76-ball 80 and David Hussey also scored at a run a ball to set up Notts' declaration.
But Sam Robson also batted through the 35-over final session for an unbeaten 28 in support of his captain as third-placed Middlesex battled hard to stay in contention in a game they somehow have to win to maintain a mathematical chance of winning the championship title.
Notts began the second day with Steven Mullaney putting the finishing touches to a gritty 125 and then surged to four batting bonus points as Adams, Hussey and Samit Patel pressed down the accelerator with some powerful hitting.
Hussey's 67 came off just 64 balls, and featured three sixes and six fours, while Patel made 47 from 65 balls, with seven fours, before being denied a fifty by a brilliant catch from Ollie Rayner.
Notts were keen to earn themselves as many bonus points as they could in a bid to stave off the threat of relegation - they began the game just seven points ahead of seventh-placed Derbyshire and eight points in front of Somerset in eighth position - but could not follow up their batting effort with early success with the ball.
Middlesex openers Rogers and Robson first blunted the new ball attack and, in some watery late summer sunshine that broke through in the post-tea session, Rogers in particular began to take the game back to Notts.
His half-century arrived from 71 balls, with seven fours, two of them eye-catching strokes through extra-cover off Paul Franks, while Robson was content to play a supporting role as he fought hard to emerge from a poor run of form that has seen him score just 123 runs in nine championship innings since he made 166 against Sussex in mid-July.
Mullaney, who resumed on 88 in an overnight total of 161 for two, reached his fifth first-class hundred and second of the season when Rogers misfielded at mid-off and he was able to scamper a quick single.
His century took him 208 balls and, by the time he skied a pull at Gareth Berg and was caught at deep square-leg, Mullaney had batted for just five minutes short of five hours, hitting 13 fours from 254 balls.
By then James Taylor had also gone, leg-before to Tim Murtagh playing around his front pad and managing only nine in front of England selector James Whitaker, who had come to Lord's in large part to watch a player who remains in the frame for a place on the winter Ashes tour.
Patel and Hussey played purposefully in a fifth-wicket stand of 60 in 13.1 overs, which gave Notts hope of a decent haul of batting bonus points, although reaching 350 seemed beyond them when Patel was spectacularly caught by Rayner at slip in the 105th over.
As Patel walked off, Rayner having plucked a thick edge off James Harris out of the air as he flung himself high to his right, Notts still required 53 runs in little more than four overs to earn themselves a fourth batting point.
By the end of the same over, however, Adams had launched his first ball high to long-off for six and Hussey had also swung a maximum over the long-on ropes. The assault continued, with the pair's fifty partnership coming up in 16 minutes and 25 balls and, remarkably, the 350 was raised with a full over to spare.
Hussey was caught behind swishing at Berg, but Notts captain Chris Read then joined Adams in a further stand of 73 in 18.1 overs, which pushed the total on past 400. The declaration came when Adams swatted Harris high to Rogers on the long-off boundary.