Chelsea's long unbeaten home record in the Premier League ended on Sunday as Liverpool earned a 1-0 victory to forge clear at the top of the standings.
Xabi Alonso's deflected first-half shot sealed a deserved triumph for the visitors, who move three points clear of Chelsea with 23 points from nine games.
Arsenal closed to within a point of Chelsea and surprise package Hull City, with a 2-0 win at West Ham United.
At the bottom of the table a whirlwind 24 hours for Tottenham Hotspur ended with a 2-0 victory over Bolton Wanderers, their first win of the season in front of new manager Harry Redknapp who replaced the sacked Juande Ramos.
Robinho scored a hat-trick as Manchester City beat Stoke City 3-0 while Aston Villa enjoyed a 4-0 win at Wigan Athletic to end the weekend in fifth place.
Portsmouth began life without Redknapp, who quit suddenly on Saturday to join Spurs, in disappointing fashion, conceding a late equaliser in a 1-1 draw at home to Fulham.
Chelsea suffered their first home reverse in the league since February 2004, a run of 86 unbeaten matches. It was also a first taste of defeat for manager Luiz Felipe Scolari since taking over at Stamford Bridge.
Liverpool have now beaten both Manchester United and Chelsea this season to underline the belief that they can win the title for the first time since 1990.
"They were unbeaten for a long time so it was a massive game and a big boost for the rest of the season," Benitez, who had never enjoyed an away league victory at either Chelsea, Arsenal or Manchester United, told reporters.
"We have shown we have character, now we must start preparing for Portsmouth because we need to get three points if we are to keep this mentality."
Liverpool moved the ball around swiftly on the wet Stamford Bridge turf from the start and drew first blood after 10 minutes when Alonso seized on a loose ball and beat Petr Cech with a shot that brushed off Chelsea defender Jose Bosingwa.
Steven Gerrard then brought a fingertip save from Cech before Chelsea began to dominate towards halftime. However, despite plenty of possession the home side only had Deco's off-target effort to show for their efforts.
Alonso smacked a free kick against the post in the second half while Ashley Cole wasted Chelsea's best chance to equalise when he sliced a volley wide late on.
Roman Pavlyuchenko scored his first league goal for Tottenham who finally recorded a victory, although they remain rooted to the bottom of the table.
Darren Bent added the second from the penalty spot after Bolton were reduced to 10 men when Gavin McCann was sent off.
Redknapp, who quit Portsmouth on Saturday to begin a salvage operation at Tottenham, faces a daunting trip to north London rivals Arsenal on Wednesday.
Arsenal left it late to defeat West Ham, an own goal by Julien Faubert and an Emmanuel Adebayor effort sealing the points. Carlton Cole was sent off in stoppage time for West Ham.