The Phillies needed the insurance in a nerve-racking ninth.
Brad Lidge - whose fall as an elite closer in Houston is often pinned on a mammoth home run he gave up to Albert Pujols during the 2005 NL championship series - faced the Cardinals slugger again with a runner on.
This time, Lidge retired Pujols on a fly to right and struck out Rick Ankiel with two runners on to earn his 20th save in 20 chances.
Howard's shot tied All-Star teammate Chase Utley for the NL home run lead. Howard's 80 RBIs lead the league, and he set a team record for most RBIs before the All-Star break.
Clay Condrey (2-1) struck out the side for the Phillies in a scoreless eighth.
Jimmy Rollins and Howard each drove in a run in the fifth, ending Philadelphia's scoreless streak at 16 innings. The Phillies hadn't scored since the ninth inning of Sunday's 12-inning loss against the New York Mets.
They never got much of chance to score against Cardinals lefty Mark Mulder. The oft-injured pitcher left his comeback start with more pain in his shoulder after throwing only 16 pitches and recording one out in the first.
The Cardinals said Mulder had left shoulder discomfort and will be evaluated on Thursday.
Mulder, coming back from two shoulder operations, made his first start since September and hasn't won a game in 25 months. The former 20-game winner struck out Rollins to start the game, then walked Shane Victorino and Utley.
He was quickly visited by a trainer and manager Tony La Russa.
After a brief talk on the mound, Mulder left the game.
Brad Thompson came in as the emergency reliever and got Howard to ground into a double play.
J.A. Happ cruised for the Phillies until he ran into trouble in the seventh. He left to a standing ovation with two runners on and one out in his third major league start.
Chad Durbin couldn't hold the lead, allowing Pujols' sacrifice fly before Troy Glaus snapped an 0-for-21 skid with a two-out RBI single that tied the game at 2.
The Phillies took a 2-0 lead against Thompson in the fifth.
Rollins, benched earlier this season for not hustling, scooted all the way to third on a triple to right that scored Ruiz.
Howard added a run-scoring single that made it 2-0.
While NL Central rivals Milwaukee (CC Sabathia) and Chicago (Rich Harden) each traded for pitchers this week to bolster their postseason chances, the Cardinals would have loved a solid outing from Mulder to show he was close to regaining his old stuff.
Mulder allowed two runs and four hits in 1 1-3 innings over two relief appearances this year. He made three starts last September and was 0-3 with a 12.27 ERA before undergoing a second operation.
Notes: Greg Luzinski had 79 RBIs at the All-Star break for Philadelphia in 1975. ... Phillies LF Pat Burrell extended his hitting streak to 10 games; Howard has his at 12 games. ... The Phillies signed three draft picks: OF Stephen Susdorf (19th round), RHP Chad Poe (27th round) and RHP Michael Bolsenbroek (42nd round).
