It was the first time the Mets played in front of a home crowd this postseason, and they did not disappoint.
Pete Alonso launched another homer off Aaron Nola, and Manaea took a two-hit shutout into the eighth inning.
Jesse Winker also went deep and Starling Marte had a pivotal two-run single to help the wild-card Mets, playing their first home game in 16 days, grab a 2-1 lead in the best-of-five series.
The Mets have never had a clinching celebration at Citi Field, which opened in 2009.
"It would be fantastic to get it done, but we've got to stay within ourselves," Alonso said.
After reaching the 2022 World Series and Game 7 of last year's NLCS, the NL East champion Phillies are on the brink of an early playoff exit at the hands of the rival Mets.
"I know it got out that I had spoken to the team," manager Rob Thomson said. "Basically it's just very simple: You come in here tomorrow, and I told them it's the most resilient club I've ever been around. That's what they're all about. They're all about toughness and fighting and playing together. That's what we need to do, and just focus on one game."
Manaea was lifted after allowing an infield single to start the eighth. The big left-hander, who blossomed into New York's ace during the second half of the season, received hearty pats on the chest from teammates and a standing ovation from the towel-waving sellout crowd of 44,093 as he strolled off the mound.
The victory moves New York one more win away from reaching the National League Division Series for the first time since 2015 -- when they made it to the World Series against the Kansas City Royals.
The Mets will try to close the series out at home on Wednesday night, with starting pitcher Jose Quintana set to face off against Ranger Suarez of the Phillies.
The Associated Press contributed to this report.
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