Australia opener Chris Rogers led a Middlesex fightback after Nottinghamshire declared at 430-7 in their Division One match at Lord's.
Rogers hit a fluent 67 not out to take the hosts to 96-0 at the end of a second day which saw Andre Adams smash five sixes in a 76-ball 80 and David Hussey also score at faster than a run a ball to set up Notts' declaration.
But Rogers and Sam Robson (28 not out) batted through the 35-over final session as third-placed Middlesex battled hard to stay in contention in a game they have to win to maintain a mathematical chance of winning the title.
The day began with Steven Mullaney putting the finishing touches to a gritty 125 before Notts surged to four batting bonus points thanks to Adams, Hussey and Samit Patel.
Hussey's 67 came off just 64 balls and featured three sixes and six fours, while Patel made 47 from 65 balls before being denied a fifty by a brilliant catch by Ollie Rayner.
Mullaney, who resumed on 88 in an overnight total of 161-2, 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.
By the time Mullaney 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 (9) had also gone, lbw to Tim Murtagh, but Patel and Hussey played purposefully in a fifth-wicket stand of 60 in 13.1 overs.
Rayner plucked a thick edge off James Harris out of the air in the slips as he flung himself high to his right, leaving Notts still requiring 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 and the 350 was raised in the end 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 which pushed the total on past 400. The declaration came when Adams swatted Harris high to Rogers on the long-off boundary.