County Championship D1, The Oval (day three, close): Surrey 378 & 7-0 v Hampshire 361-6dec
Nic Pothas hit an unbeaten century, his third Championship ton of the season, as Hampshire produced a fine first innings response at The Oval.
The in-form wicket-keeper hit 15 fours and two sixes, building on a third wicket stand of 107 between Shane Watson (88) and John Crawley (42).
Their efforts, plus an unbeaten 49 from Adrian Mascarenhas, helped the visitors declare 17 runs behind Surrey.
The hosts had extended their lead by another seven runs by the close.
Pothas' century was his third hundred in four games, and he reached three figures with a swept six over midwicket off Nayan Doshi, which signalled the end of the innings.
Watson - a contender for a spot in Australia's side for the final Test at The Oval - played a watchful innings from 191 balls as Hampshire batted the possibility of a Surrey win out of the game.
With the first day washed out the outcome of the match will now depend on whether the two captains can engineer a finish.
With Surrey flirting with relegation, the hosts will have to force the pace on the final morning if they are to get anything tangible out of the match.