HARRISBURG, PA. -- There was a capital city that once had a baseball team called the Senators. It was a city known for long summers of humid days and dull, motionless nights; a city on a river where the most popular spectator sport, after the Senators left, was politics.

This capital city 100 miles north of Washington, D.C., still has its humidity and politics, but suddenly, unexpectedly, it is once more a red-hot baseball town.

Harrisburg not only got baseball back after a 35-year absence, but the Harrisburg Senators now are in a best-of-five playoff series for a shot at the Eastern League crown.

Few expected this town or this team to pull it off. It's a city known more for its accidents (Three Mile Island) than its achievements. And the team started the year near the bottom of the league.

But through persistent city officials, a 5,000-seat stadium was built on an island in the Susquehanna River and a minor league franchise coaxed. Then the team started streaking and captured the hearts of local fans.

The team, a Class AA farm club of the Pittsburgh Pirates, moved here this year from Nashua, N.H., where it finished last three years in a row. It's the first time pro baseball has been in Harrisburg since the 1952 Harrisburg Senators, perennial cellar-dwellers in the old Interstate League, played their final home game to a crowd of 301 and finished the season 42 games out of first place.

Last year in Nashua total attendance for the 140-game regular season was 78,000. This year in Harrisburg it was more than 212,000, double an optimistic preseason goal and second in the league only to the Albany (N.Y.) Yankees.

The Senators have the league's leading hitter in 24-year-old outfielder Tommy Gregg (.368). First baseman Ron Johns made national news by going six for six with three home runs in three consecutive innings. Second baseman Jim Reboulet hit safely in 32 straight games.

"I can't tell you how many people come up to me and say this is the absolute best thing that has ever happened to Harrisburg," says Senators General Manager Rick R. Redd. "When we started here, we wanted to make the ballpark a social event so that no matter what kind of team we had, people who came out would come back. But there has been more involvement, even by people who were never baseball fans, than we ever hoped for."

On Second Street, a one-way downtown strip, restaurants and bars once empty after working hours now are full before and after games.

The Sandwich Man, a one-room hole-in-the-wall sub shop that used to boom only at lunchtime, is busy with players and fans on game nights. Jeff Whitcomb, who's been at the same location for more than four years, says the team definitely improved his business.

George Wise, who runs Shoe's 'N Shine, just off the town square, says his customers talk Senators baseball constantly. "Harrisburg's a tough town," Wise said, "but this town is up for them, very enthusiastic."

State Rep. Peter C. Wambach grew up in Harrisburg. "There is no doubt this team was the spark for a lot of positive change," he said. "They have made believers out of nonbelievers. They have provided fabulous family recreation. When I sit in those stands and look down the third base line at the thousands of people, I realize what a focal point the team has become."

RiverSide Stadium is kept clean; vendors banter with fans, and everybody sings "Take Me Out to the Ball Game" during the seventh inning stretch.

In the playoffs, the Senators are playing their archrivals, the Reading Phillies, a Philadelphia farm team based about an hour's drive from here. If the Senators win the series, they'll play for the league title.

But win or lose, supporters say, their return and first season here is a major league victory for a born-again minor league town.