"Playing winning baseball this late in the season, that's what we all play for," said Francisco, who had been toiling for AL also-ran Cleveland before coming to Philadelphia on July 29.
He has started five games in the outfield for the Phillies, who won for only the fourth time in 12 games to maintain their 3½-game lead over Florida in the NL East.
The Cubs, meanwhile, have lost five of six to trail St. Louis by three games in the NL Central -- and frustration is setting in for the two-time defending division champs. Manager Lou Piniella got upset after a question about top relievers Gregg and Carlos Marmol, who walked in an eighth-inning run.
"You want to manage and lose five out of six and see how you feel?" Piniella, his voice rising, asked a reporter. "You come up here and you sit here and let me ask you the question and let me see what your emotions are."
Francisco lined a 1-1 pitch into the basket that hangs over the left-field fence. It was the 11th homer allowed this season by Gregg (4-4), who was acquired from Florida in the offseason to replace Kerry Wood. Earlier this month, he blew saves in consecutive games, both on home runs.
"Keep the ball in the ballpark," he said. "I've got to figure out a way."
Francisco is batting .345 with six homers and 12 RBI in his last 16 games with Philadelphia and Cleveland combined.
"It feels good to get a big hit like that in a pennant race," he said. "I'm excited to be here."
And the Phillies are excited he's their teammate. Tuesday, nobody was happier than closer Brad Lidge, who coughed up a ninth-inning lead.
"He's been hitting the ball really well ever since he got here," Lidge said. "We got Cliff Lee but we got another really good player, too."
Perfect in 41 save opportunities last year, Lidge has blown seven saves in 28 tries this season. Kosuke Fukudome drew a leadoff walk, advanced on Ryan Theriot's sacrifice bunt and scored the tying run on Milton Bradley's line-drive single to right. Lidge has a 7.29 ERA; it was 1.95 in 2008.
"He's our closer," Phillies manager Charlie Manuel said. "We've got to get him through this."
Francisco's shot made a winner of Scott Eyre (2-1), who fell out of favor in Chicago last season and was traded to Philadelphia, where he went on to win a World Series ring. After Eyre worked 1 1/3 perfect innings, Chad Durbin, fresh off the disabled list, pitched a hitless 12th for his second save.
The Cubs took a 2-0 lead in the third on Jake Fox's RBI single and Alfonso Soriano's sacrifice fly. Rich Harden made the lead stand into the sixth, retiring the first 16 batters before walking Carlos Ruiz. Then, with two outs, Jimmy Rollins broke up the no-hitter and tied the game with a homer into the right-field bleachers.
Rollins is batting .325 with eight homers and 27 RBI in 151 at-bats since snapping a career-worst 0-for-28 streak.
Harden allowed only one other hit, Ryan Howard's single, in seven innings.
The Phillies took the lead in the eighth when Marmol hit a batter and issued three walks, the third to Howard with the bases loaded. Opponents are batting only .166 against Marmol, but he has walked 52 batters and hit 11 others in 53 2/3 innings.
"Every time I walk the first batter, it kills me," Marmol said. "It's mechanics, that's all it is. I'm working ... to get it back."
Philadelphia starter J.A. Happ, who leads the NL with a 1.84 road ERA, allowed seven hits and two runs in six innings.
- Leading 3-2, the Phillies thought they had scored a ninth-inning insurance run on Ruiz's homer down the left-field line. But the umpiring crew used replay review and correctly ruled it a foul ball. It was the first video review ever at Wrigley Field.
- Cubs 3B Aramis Ramirez (left shoulder soreness) received a cortisone injection Tuesday morning to reduce inflammation and hoped to be back in the lineup by Thursday or Friday.
- Phillies All-Star RF Jayson Werth, hitless in his last 14 at-bats and mired in a 3-for-26 slump, was out of the starting lineup for a second straight game. He struck out as a pinch-hitter in the 12th.
- Cubs 2B Jeff Baker had four hits, all singles, tying a career high.