Swindon deposed Southend from second place in npower League Two on goal difference courtesy of a comfortable 4-1 victory at Roots Hall.
The visitors opened their account after nine minutes when Ronan Murray's effort cannoned off the right post and Matt Ritchie drilled in the follow-up from 18 yards.
Things got better for Paulo Di Canio's team six minutes later when Ritchie's deep cross from the right found Joe Devera at the back post and he headed back across goal for an unmarked Jonathan Smith to score from six yards.
Southend pulled one back after 34 minutes when Sean Clohessy's cross was cleared by Smith to Jean-Paul Kalala, whose 25-yard shot went in off the left post.
But Swindon restored their two-goal advantage in the 27th minute when Devera had a free header at the back post from Ritchie's corner from the right.
Substitute Billy Bodin had only been on the pitch five minutes when he made it 4-1 in the 55th minute. Ritchie's cross from the right was palmed by Glenn Morris into the striker's path and he shot low into the centre of the goal from 16 yards.
Southend dropped a place to third following their heaviest home defeat of the season, with Swindon climbing from sixth spot.
Southend 1-4 Swindon: Match Report - view commentary, squad, and statictics of the game as it happened.