Warwickshire were reduced to 144-3 in pursuit of a victory target of 515 at stumps on day three against Somerset at Taunton.
Rookie left-arm spinner Jack Leach claimed 3-25 in 15 overs after Warwickshire openers Varun Chopra and Will Porterfield had put on 108.
Leach accounted for Porterfield (36) and later removed Jim Troughton (17) and Ateeq Javid (0) with successive balls to put Somerset in a strong position.
Chopra remained unbeaten on 81 at the close with Warwickshire still 371 runs short of their target.
Somerset had earlier advanced their second innings from 46-1 at the start of the day to a mid-afternoon declaration at 266-4.
England opener Nick Compton led the way with 105 not out - his 19th first-class century - and received good support from in-form Alviro Petersen (43) and Craig Kieswetter (59no).
Warwickshire were without all-rounder Rikki Clarke due to a muscle injury, while seamer Chris Woakes was the most successful of the visiting attack with 2-50.