Democratic City Councilman Jose Marco Serrano defeated State Senator Olga A. Mendez yesterday in a historic battle for the 28th Senate District, which includes neighborhoods in the South Bronx, East Harlem and Roosevelt Island.

Serrano, 32, son of a longtime Bronx Democratic congressman, Jose E. Serrano, effectively ended the reign of Mendez, 79, the first Puerto Rican woman elected to a legislature on the U. S. mainland. He also affirmed the popularity of the Serrano name over that of Mendez, a name that has become synonymous with Puerto Rican politics in the United States.

Serrano easily bested Mendez, winning 47,915 votes, representing 81 percent, while his opponent got 10,365 votes, a mere 18 percent. The district is one of the city’s most heavily Democratic, with 10 registered Democrats for every Republican.

At Giovanni Restaurant on the Grand Concourse Tuesday night, as Jose M. Serrano was led in by his father, his supporters erupted in a loud applause.

Democratic Party bigwigs surrounded the newly elected state senator. Congressman Charles Rangel, D-Harlem, Bronx Borough President Adolfo Carrion, Jr. and State Senate Minority Leader David Patterson, D-Harlem, were among his entourage.

“Jose, Jose, Marco, Marco, Marco,” the crowd shouted as many struggled to hug him or shake his hand.

With the proud look of a happy father, Congressman Jose E. Serrano introduced his son. “Though I know you are not interested, but I also got elected tonight,” he said. “Ladies and gentlemen, I hereby introduced the newly elected senator for the 28th Senate District, my son, your friend, and our representative, Jose Marco Serrano.”

The new state senator then said, “I want to say something that is very important to me and this community. That is to thank Sen. Mendez for her 26 years in politics. I want to thank her for what she has done to represent Latino interests. And I pledge to continue in that legacy of service to our community.”

In a later interview, Serrano said his first priority in Albany “is to work closely with my colleagues and increase the minimum wage in this state. I want to see how we can increase it to $7.50 minimum, which is not even enough for our citizens.”

The 28th State Senate District used to be composed largely of East Harlem and northern Manhattan, until it was redrawn after the 2000 census. Consequently, a large portion of the south and west Bronx accounted for most of the district’s voters. This helped Serrano, a city councilman who has for three years represented 40 percent of the voters in the newly drawn senate district.

Serrano also had great support from Democratic heavyweights in Manhattan and the Bronx. Sen. Hillary Rodham Clinton, Bronx Borough President Adolfo Carrion, Jr., former Bronx Borough President Fernando Ferrer and Assemblyman Jose Rivera, the chairman of the Bronx Democratic Party, all endorsed Serrano.

He also had the backing of his father and the entire Bronx Democratic organization, which provided financial support.

The seat featured prominently in the calculations of both Republican and Democratic leaders over which party will control the State Senate in Albany in coming years.

The two parties gave significant financial support to their candidates. Mendez’s campaign received around $200,000 from state Republican leaders. Serrano had raised nearly $100,000 in July, according to records posted by the state Board of Elections, and he spent about $160,000 in the Democratic primary. He told The New York Times early October that he hoped to spend $150,000 in the general election.

Last July, Mendez was fined by the state Board of Elections for failure to submit required campaign filings since September 2002. The board slammed her campaign with judgments of $500 per violation -- the maximum allowed by law -- for each of seven reports never submitted.

The race was particularly painful for Puerto Ricans, especially some older ones, who felt bad that they had to choose between two of their most prominent political families.

“It’s sad that a Puerto Rican who has served his community well ran against another Puerto Rican who is a well established politician and part of the political history of Latinos in this country,” said Justino Rodriguez, 59, a retired education supervisor and a member of the Bronx’s Community Board 1, which includes part of the Senate district.

Mendez’s December 2002 party switch from Democrat to Republican was a major factor in her defeat, according to many observers.

At that time, she said the switch would enable her to attract more money for projects for her constituency.

“In the interests of my constituency, I have decided to switch my registration,” Mendez said in 2002. “The Republicans in Albany have reached out to me and to other Puerto Ricans in good faith, and I am accepting their call. My constituents can best be served by working with the majority party, not trying to obstruct the business of government.”

Former State Sen. Pedro Espada, Jr. of the Bronx, who made a similar switch in 2002, lost the general election two years ago. City Councilman Reuben Diaz Sr., who had been selected by Bronx Democratic officials less than two weeks before the primary, defeated Espada in the elections.

Before yesterday’s election, some political experts said Mendez faced an uphill task in keeping her seat, especially in a presidential campaign year.

“People are still going to come out and vote for the presidential elections at the same time, and Bush is not popular among Latinos in New York,” explained political consultant Bob Liff. “If she wins, then she’s an absolute phenomenon. But that party switch cannot help her in a largely Democratic area.”

Fred Siegel, a conservative writer and professor at Cooper Union, said, “The national dynamics don’t help, but she was probably going to lose anyway, because she’s running as a Republican, and it’s very hard to make that switch.

“Most of her supporters were conventional Democrats. Her personal base may swing with her, but it’s not large enough.”

“I can’t see how Mendez wins,” said Adam Silvera, a Democratic district leader in lower Manhattan. “I think she will be a casualty, having switched parties. Party- line voting is certainly more likely in this election.”

Some people in the district saw the election in simpler terms.

“This is more or less a popularity contest or, if you like, a generational battle,” said the Rev. Eddie Lopez, Jr., pastor of the La Resurreccion United Methodist Church in Melrose, the Bronx.

“It’s an interesting battle,” Lopez said. “Unfortunately, it’s not one that would make a large difference. Politics in this area is no longer about people, but about political self-preservation. How do I stay in office or get re-elected seems to be the chief concern of politicians here.”

Serrano is not a “people person,” Lopez said. “I don’t think the guy enjoys being with people. Maybe he’s just in the wrong place. The last time I saw him, it was his father who spoke and he was just waving at the people.”

A Bronx Democratic Party spokesman disagreed with this view. “We’re supporting Serrano because he alone can provide effective representation for the Bronx and East Harlem communities,” said Luis Martinez, executive assistant to Jose Rivera, chairman of the Bronx Democratic Party.

“Olga Mendez is a Republican, and the Republicans are hurting us,” Martinez said. “They are doing so in the funding formula for the state budget, in not providing enough money for the education of our children in public schools and by not finding solutions to the city’s problems.”

Martinez praised Serrano saying, “He’s been there working for the district too. As a council member, he’s been a good navigator of the communities, especially on issues dear to our hearts.”

He said of Mendez, “It’s unfortunate she turned Republican and decided to associate herself with policies that are hurting our communities.”

Before Serrano’s election to the City Council in 2001, he was a member of Community Board 4 in the Bronx. He graduated from Manhattan College in 1995 and worked with the New York Shakespeare Festival after his graduation.

Mark Berkey-Gerard of the Citizens Union said Serrano’s most difficult moment in the City Council was when he voted in favor of building a controversial water-filtration plant in Van Cortland Park in the Bronx. “It was not a popular move in his district,” Berkey-Gerard added.

In a community forum held at La Resurreccion United Methodist Church a week before the general election, Serrano emphasized repeatedly the party switch by Mendez.

“The fact is that the Republican Party and Republican leadership in Albany have failed people in this area,” Serrano said.

“And by switching to the Republican Party, Olga Mendez has given up fighting for the people in this district,” he continued. “They have failed to come up with a fair funding formula for the schools in this city. We need a senator who will go to Albany and fight for these things, not to give up, switch to becoming a Republican and vote their way.”