Cockermouth drew first blood in the crunch confrontations with Carlisle which are staged over 48 hours.
Last night the Sandair side were convincing winners by 57 runs in the North Group T20 game.
Tomorrow afternoon they go head-to-head in the crucial Premier Division clash at Edenside with Carlisle unbeaten, and eight points clear of their rivals.
But in a psychological blow Cockermouth earned their second win of the season in knockout cricket against a Carlisle side who have won every Premier League game.
This T20 success follows their victory last month in the quarter final of the Higson Cup.
Carlisle won the toss and decided to field so when they kept Cockermouth to 127-8 must have fancied their chances.
But they faltered badly and were bowled-out for 70 with Matthew Siddall continuing his great week.
The left-arm spinner from Blackpool followed up his 11 Championship wickets for Cumbria by taking 4-9 from his four overs.
Part-time spinner Gareth White weighed-in with 3-18 from four as Carlisle struggled. Only Nico Watt (18), batting at seven and opener Tom Benn (12) reached double figures.
No such restriction for Cockermouth as Greg Platten (42), Alex Grainger (35) and skipper Matthew Sempill (20) scored freely.
Chris Blythe (2-23) was the most successful Carlisle bowler.
Workington have the West group stitched-up and recorded a fourth win when they beat Whitehaven by 45 runs at the Playground.
After winning the toss and electing to bat, a rather different Workington line-up saw Matthew Gorley opening and top-scoring with 36 while the man with most career runs, Kristian Moffat went in at nine and made 22 not out off 16 balls.
Liam Hazzard (19) and Josh Burns (18) also chipped in as Workington finished on 143-8.
Timycen Maruma, the Whitehaven professional took 4-12 from his four overs and Stephen Holliday took 2-17.
Whitehaven only managed 98-7 in reply with Maruma top-scoring with 30 from 31 deliveries, and included three fours and a six.
The home side were also aided by 30 extra, 19 of which were from wides. Workington pro Lahiru Dilshan took 2-7 from his four overs.
There was disappointment in the South group where Lindal Moor conceded their game against Dalton and section leaders Haverigg were unable to raise a team to play Furness.
