The second-placed Foxes adapted better to atrocious conditions to score twice in thefirst half and they then coped easily with Portsmouth's pressure.
Pools of water made the match a lottery but referee Andy Hall decided the game couldgo ahead although both sides struggled to show the sort of form that had made themthe first division's best two sides.
Leicester took the lead in the 13th minute when a long kick down the pitch bygoalkeeper Ian Walker bounced through to Paul Dickov and his low centre was turned inby James Scowcroft.
Leicester always looked more likely to score again and so it proved in the 39th minutewhen Muzzy Izzet took a corner on the left and big defender Matt Elliott headed in at thenear post.
Former West Ham keeper Shaka Hislop prevented Dickov adding a third just before thebreak and when rain fell again during the interval there were major question marks aboutthe match being allowed to continue.
But Leicester held on comfortably and Scowcroft came close to adding a third in the 60thminute with a header from Izzet's pass which hit the bar.
In stoppage time substitute Mark Burchill went around goalkeeper Walker but could onlyshoot into the side-netting while at the other end Trevor Benjamin got the better ofHislop but stumbled as he prepared to shoot into an empty net.
Portsmouth manager Harry Redknapp said after the match: "The match should neverhave been allowed to go ahead. It was nonsense, crazy.
"I told my players at half time just to kick the ball forward, so what type of football isthat?"