PITTSBURGH, SEPT. 5 -- The Pittsburgh Pirates and New York Mets wrestled through two games' worth of September baseball at its tension-filled best tonight before 49,793 at frenzied Three Rivers Stadium. It was one of those knee-weakening evenings on which a pennant race can turn -- and when the Pirates had completed a dramatic sweep, the National League East indeed had a new feel to it.

One of the Pirates' heroes was Barry Bonds, whose 100th RBI provided a sudden-death, 1-0 victory in the opener. But the others were Zane Smith, Jeff King, Neal Heaton, Bob Kipper and Ted Power. Virtually everyone plays a part on this Pittsburgh club -- 19 Pirates pitchers had won games entering tonight, while eight had registered saves -- and rarely has that been in better evidence.

Smith pitched a one-hitter in the opener, then the Pirates tacked on a 3-1 victory built upon the first two-home run game of King's brief career.

In Game 1, Smith faced just 29 batters and didn't allow a hit after Keith Miller's single leading off the game. The crafty but underwhelming, 29-year-old left-hander issued only one walk (to Miller) and retired 27 of the last 28 hitters he faced, including the final 19.

"That's as well-pitched a game as you're going to see," Pirates Manager Jim Leyland said. "Zane Smith was simply outstanding.

"It's a huge lift for us."

Bonds's fly ball off reliever John Franco with one out and the bases loaded in the ninth inning landed beyond a drawn-in outfield to score Gary Redus after 17-game winner Frank Viola had matched zeroes through eight innings with Smith, who now has 17 scoreless innings in a row.

The Mets began the day as the highest-scoring team in the NL. But their lone run of the night came on Darryl Strawberry's 31st homer, off Heaton in the fourth inning of the second game.

"They had their crowd behind them" -- the Pirates' largest of the season and biggest non-opening day gathering in 13 years -- "and they stuck it to us," New York shortstop Howard Johnson said.

"They did what was required and we didn't. We both got some good pitching, but they got a little more offensive production. It didn't take much."

Pittsburgh has won five straight games and swept its fifth doubleheader in five attempts this year to improve to 80-56 and up its NL East lead to 2 1/2 games. And, if the Mets (77-58) weren't acutely aware of it already, they learned this two-team sprint to the finish will be a tight, draining one.

"If anything, this tells them that we're for real and they're going to have a battle on their hands," said Smith, who has endured some trying times since he underwent elbow surgery two years ago.

But he's 10-7 on the season, 4-0 with a 1.54 ERA in five starts with Pittsburgh since being acquired from the Montreal Expos last month, in great part because of past effectiveness against the Mets. The one-hitter is the first of his career and the first since 1987 against the Mets -- who also lost a 1-0 game Tuesday in St. Louis.

"It's a great feeling," Smith said. "It's hard to describe. . . . I got behind the first hitter, then I was ahead in the count for the rest of the night."

Viola struggled mightily but managed to hold the Pirates scoreless by escaping one jam after another. Pittsburgh went zero for six with men in scoring position and stranded seven runners through the first three innings alone, wasting a bases-loaded, one-out opportunity in the third.

But Viola, after a laborious 128 pitches, was lifted for a pinch hitter in the ninth. And Franco was in trouble almost immediately after taking the mound.

He allowed a leadoff single to Redus, then watched as catcher Charlie O'Brien threw past shortstop Johnson at second base after fielding Jay Bell's sacrifice attempt.

Andy Van Slyke advanced both runners with a well-executed bunt, and the Mets walked Bobby Bonilla to fill the bases. That brought up Bonds, who slapped a two-strike fastball on the outside corner over the head of left fielder Kevin McReynolds with a towering fly that landed on the warning track for what officially went as a single.

"The 100th {RBI} was the biggest one," Bonds said. "These are the kinds of nights when you win pennants, and we took a step in that direction."

King helped the Pirates take another meaningful stride later. The second-year third baseman connected for a homer in the first off Bob Ojeda -- who fell to 7-6 in his first start since July 26 -- then provided a two-run blast in the third for a 3-0 Pittsburgh lead.

Strawberry got the Mets to within 3-1, but that was it for the New York offense. Heaton (12-8) limited New York to five hits in five innings, and Kipper and Power finished with four innings of two-hit relief.

"We're getting contributions from everyone," Leyland said. "It's a nice feeling. . . . We can't get carried away, though. It's just one day, and there's a long way to go." But as New York Manager Bud Harrelson said between games: "It felt like a lot more" than one day to the Mets.

Tonight's games were the first of eight down-the-stretch meetings between these closely matched but very disparate clubs. The Mets are the team that was supposed to be in this position, having finished first or second each year since 1984.

But the Pirates are adding maturity to talent, and they're as unyielding as the City of Steel that houses them. They battled New York into late July two years ago before fading into a 15-game hole. They promise to be harder to shake this time around.

Pittsburgh has been in first place for all but 17 days this season, and the Pirates persevered through the Mets' midseason charge that threatened to steamroll the rest of the division. "They're not afraid of us anymore," McReynolds said.

Said Bonilla: "We're going to fight it out with them right to the end. They may get us down or we may get them down. But whatever happens, we'll keep scratching and clawing and biting and gouging their eyes out until the last day. Then we'll shake hands and say the best team won. I think it'll be us."

Notes: The Pirates added eight players from their Class AAA Buffalo farm club today, giving them 36 players in uniform for the doubleheader -- and one of them was left-hander Jerry Reuss, 41, his second stint with the Pirates. The left-hander was 61-46 during 1974-78, including an 18-11 record for the 1975 East Division champions.

He has become a baseball rarity, a major-leaguer in four decades. He broke in with the 1969 Cardinals.