While the Lions were being beaten by a Ricky Rawlins inspired Sarisbury Athletic, Calmore trimmed earlier table toppers Hook & Newnham Basics by three wickets to move into second spot.
Hook were never allowed to dictate the terms and were soon 12-3 against the miserly left-arm of Steve Wright (1-18) and Liam Newton (3-31), the in-form Richard Willcock and skipper Matt Love both bagging ducks.
Harry Warner (26) and Jordan Hobday (32) got the scoreboard moving, while Rhodes Franklin (19) added some useful runs before Hook were 126 all out, Mark Lavelle and Mike West picking up two wickets each.
Calmore wobbled at 19-2, but improved through Ben Johns, left, (36) and James Manning (26), only for left-arm spinner Rhodes Franklin (3-29) to reduce them to 73-5.
But largely due to Ben Perry (16) and Mike West Calmore got home seven wickets down.
Ventnor lost six wickets for 22 runs to spin pair Jody Brown and Matt Bampton as they tried in vain to chase down Old Tauntonians & Romsey’s total of 150 at the Romsey Sports Centre.
The islanders appeared in good shape at 69-2 with Martin Blackman (25) and Tom Friend (23) at the crease.
But Brown, who finished with figures of 5-15 off his ten overs, dismissed both batsmen before removing the entire Ventnor top order as the visitors plunged to 91-8.
Bampton’s equally miserly spell of 2-15 came at a stage when the Ventnor tail wagged, lifting their reply to 130 all out, 20 runs adrift of the target.
Earlier, OTs collapsed in a similar, but no so dramatic style.
Ian Woodhall (30) was prominent before Harry Tulk (41) and Brown (18) raised the score to 106-3 before James Cheek (4-33) and Charlie Sammons (3-22) crated inroads and reduced OTs to 150 all out.
OTR visit Portsmouth on Saturday, the city hosts struggling in second from bottom place but being bolstered by the arrival of former Hampshire 2nd XI all-rounder Fraser Hay and Andy Moon, from Australia.