Division One pace-setters Somerset came up against stubborn resistance from Hampshire on day two at the Utilita Bowl.
The early leaders lost seven wickets for 113 as they were bowled out for 288, then saw a lead of 50 evaporate in Hampshire's second innings.
Hampshire reached 146 for one to lead by 96 at stumps, Nick Gubbins unbeaten on 70.
England hopeful James Rew was first to fall for 86 in the morning session but saw his Test ambitions trumpeted by head coach Jason Kerr.
"He is a good enough player to play international cricket. He has scored a lot of runs over a lot of years," said Kerr, who has resisted the urge to use Rew as an opener, the position most likely to need filling this summer.
"If he opens the batting then great, I appreciate the middle order is quite stocked at international level, but a player of that talent should be knocking on the door.
"But we have to do what is right for the team. What I don't want to do is compromise his opportunity of playing for England. Could he do that at the top of the order for England? Absolutely."
At Edgbaston, Essex and Warwickshire were vying for control of a nip-and-tuck contest. The Bears were bowled out for 190 following their day one travails, with Sam Hain left high and dry on 88 not out.
Essex then reached 110 for three, with Ethan Bamber striking twice.
In Division Two, ball continued to dominate at Bristol, where 23 wickets have fallen in two days of Gloucestershire's clash with Lancashire.
The Red Rose were looking dominant at 140 for two in reply to 136 all out, but ended up folding for 240 as Matt Taylor took career-best figures of six for 43.
Lancashire replied with three breakthroughs in eight overs after the turnaround, including an 18th of the season for the evergreen James Anderson. Gloucestershire will resume on 58 for three, trailing by 46.
Elsewhere, an unbroken stand of 131 between Nathan McSweeney (87no) and James Sales (78no) kept Northamptonshire in the battle against Middlesex.
Middlesex were finished off for 341, nine short of a third batting point, but had their opponents wobbling at 98 for four before Australia's McSweeney came together with rising star Sales to swing the momentum back.
