Leicestershire 183 for 6 (Ackermann 58*, Ronchi 57, Plunkett 3-42) beat Yorkshire 182 for 5 (Kohler-Cadmore 75, Marsh 60) by four wickets
Leicestershire completed a second win in two days to put themselves firmly back in the hunt for quarter-final qualification, beating Yorkshire by four wickets with two balls remaining.
A spectacular half-century from New Zealand international Luke Ronchi, hit off just 19 balls and including seven fours and three sixes, set the Foxes on their way, and although they lost wickets regularly in an increasingly nervy reply, Colin Ackermann's unbeaten 58, made off 47 balls, saw them cross the line in the final over.
"The batting was outstanding. Luke Ronchi has been unbelievable for us, and although Ackermann has had a bit of a lean patch over the last few games, he showed what a class player he is," Leicestershire's captain, Clint McKay, said.
"I think the bowlers fought back well towards the end, though I was a bit disappointed with how we went about our work in the field earlier in their innings, we weren't at our best. But the boys keep bouncing back, and to keep it to 182 when it looked like they were going to get over 200 was a great effort."
Remarkably, it was their first victory at home in the competition this season, with their previous five wins all coming away from the Fischer County Ground. Their two remaining fixtures see them face Derbyshire at home next Thursday, before they travel to Trent Bridge to play Nottinghamshire the following evening.
Yorkshire, who arrived with their spirits - and chances of qualification - lifted by beating Roses rivals Lancashire at Headingley the previous evening, must now beat Northants at home on Thursday, their final group fixture, to have any chance of qualifying.
Yorkshire's total was based on an explosive 75 from Tom Kohler-Cadmore, the right-hander's best T20 score since joining Yorkshire from Worcestershire, made from just 40 balls.
Placement and timing was the key, particularly through the off side, in a 30-ball half-century which included ten fours. Two maximums followed, muscled through wide midwicket off Callum Parkinson, but the young left-arm spinner had his revenge when he deceived and bowled Kohler-Cadmore in the last of his four overs, his 14th wicket in the competition this season.
Their other major contribution was made by Shaun Marsh, whose half-century came seven balls more slowly, with four of his seven boundaries cut behind square on the off side. Having been 129 for 3 off 14 overs, a total of 200 looked well within their capabilities, but tight Foxes bowling, notably from Matt Pillans, and an unexpectedly effective four overs from occasional offspinner Aadil Ali, took some of the pressure off the Leicestershire batsmen.
Ronchi's wonderfully clean hitting reduced it further - the highlight an uppercut six high over third man off David Willey - and although he slog-swept Azeem Rafiq to into the hands of Jack Leaning on 57, Ackermann's sensible innings ensured Leicestershire got over the line.
Yorkshire coach Andrew Gale: "It was a real blow to lose this match. I felt on this occasion it was our bowlers who didn't perform as well as they should, we bowled too many four balls. We knew Ronchi was the danger man, and he duly got them off to an explosive start. I was actually pretty pleased with our score, but giving away too many boundaries cost us dearly.
"We've played some good cricket in the competition but we've not put it together in both disciplines consistently enough."