Middlesex had started the week 30 points behind second-placed Glamorgan.
They realistically needed victory in Manchester and for the Welsh county to lose to Derbyshire and after the first day was washed out, lost more time due to a wet outfield on the second.
In such conditions, it was an easy call for James Anderson, captaining the Red Rose with Marcus Harris back in Australia, to put the visitors in.
Only five overs were possible before rain arrived, but that was still enough for Lancashire to strike twice.
Bailey had Sam Robson well caught at second slip for nine before Anderson drew the edge from left-hander Luke Hollman with a probing ball across him that was snaffled up at first slip as he went for a duck.
More rain forced a two-hour stoppage before an eventful six-over period in which the visitors rattled up 48 runs.
Captain Leus du Plooy and de Caires helped themselves to three boundaries apiece, aided by some generous bowling from their hosts.
When play resumed again at 16:00 BST, the pair brought up a 50-partnership before du Plooy was caught behind off Tom Aspinwall for 22.
And it was two in two balls for the young seamer as he got one to bounce on Ryan Higgins, which he could only fend to first slip.
De Caires then put on another half-century stand with Geddes, as he went to his fifty off 65 balls but departed shortly after as he drove loosely at Bailey.
Part-time medium-pacer Josh Bohannon then bowled Joe Cracknell for six with his first ball to leave Middlesex wobbling at 132-6.
But Zafar Gohar offered good support to Geddes, who dug in for a fifth half-century of the summer off 80 balls, highlighted by three pulled sixes over the short leg-side boundary, until those two late Lancashire strikes.
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