Gloucestershire 158 (Hammond 67, Parkinson 5-45) and 5 for 1 trail Leicestershire 451 (Harris 148, Ackermann 57, Hill 56) by 288 runs
Group Two leaders Gloucestershire are in danger of slipping to a second consecutive defeat after Leicestershire took firm control on the second day of their LV=Insurance County Championship match.
After seeing their points advantage shrink when they were beaten by an innings by Surrey last week, Gloucestershire were bowled out for 158 in reply to Leicestershire's 451 as left-arm spinner Callum Parkinson - seemingly none the worse for a painful blow on the left forearm while batting - took 5 for 45 on a turning pitch with the added hazard of variable bounce.
Parkinson struck again after skipper Colin Ackermann enforced the follow-on, having Chris Dent caught at slip in the last over of the day, and Gloucestershire will resume 5 for 1, needing a further 288 to make Leicestershire bat again.
"I'm delighted with the way it has gone and it was the icing on the cake to get their skipper there at the end," Parkinson said. "The lads are all pumped - everybody's chipped in.
"With the ball it was a matter of being patient and putting the ball in the right areas because we knew there was a bit of spin on offer. The wicket against Middlesex last week flattened out in our favour, but fingers crossed this one keeps a bit in it. With two days to go we are in a great position."
Only opener Miles Hammond, who made 67, offered profitable resistance in their first innings and there were three wickets also for Ackermann's offspin as Gloucestershire's struggles on spinning tracks continued on from last week's thrashing at The Oval.
Parkinson's figures were his best since he took 8 for 148 against Worcestershire in 2017, his only other haul of five wickets or higher.
Resuming on 357 for 5 on the back of Marcus Harris' 148, Leicestershire achieved their first objective by taking their score past 450, rejecting the temptation to chase a fifth batting bonus point in favour of a more cautious approach.
Harry Swindells made a useful 37 before nicking Tom Smith's left-arm spin to slip and Ben Mike was trapped in front for 24, but it was only after lunch that the innings fell away, the last three wickets going for 15 in 29 balls.
Hammond, who had Chris Wright caught tamely off a full toss, took two wickets in an innings for the first time in a first-class match with his offspin.
Opening the batting, Hammond began aggressively and Gloucestershire raced to 48 from 13 overs before Ackermann struck with his first ball, turning one past the outside edge to bowl the left-handed Dent.
New man Glenn Phillips, the New Zealand international on debut ahead of his Vitality Blast stint, went after the offspinner, launching a slog-sweep T20-style for his third boundary against him, but came unstuck against Parkinson, falling to a brilliantly executed catch on the run by Harris at mid-on.
Tom Lace, caught behind off Ackermann, Ian Cockbain, caught at second slip off Parkinson and Ryan Higgins, bowled first ball by the left-arm spinner, all went cheaply before Hammond's fell to Parkinson attempting a reverse-sweep, the ball keeping low and creeping under his bat.
Smith bowled by Ackermann with another one that did not bounce as anticipated, and after Jonny Tattersall, whose loan spell from Yorkshire was extended to cover this match, miscued Wright to midwicket, Parkinson claimed his fifth scalp as Josh Shaw went leg-before.
Ian Harvey, Gloucestershire's coach, said: "It's very tough to bat out there. There is some turn and variable bounce but we're up against some quality bowlers and it's not meant to be easy. We've got two days to bat, we've got to dig in, fight hard, not give our wickets away and make it tough for them. The lads have to show some character. The boys have shown that in the past and they will have to do that again tomorrow."
