SAN FRANCISCO — The throng of Asian-American donors drew closer, drinks in hand, to hear Barack Obama's sister describe the wide arc of his life: beyond politics and Chicago, into his childhood in Indonesia and Hawai'i.

To many in this crowd Obama's Asian-American half-sister, Maya Soetoro-Ng, represents yet another aspect of Obama's identity that makes him unique as a presidential candidate, although it has been underplayed amid the excitement surrounding his shot at becoming the first black president.

"It would be the first time that the first family is comprised in part of Asian-Americans — as well as African-Americans, of course," said Keith Kamisugi, a coordinator with Asian-Americans for Obama. In early June he organized a fundraiser along with two other Obama events focusing on Asian-American voters in San Francisco.

Discussion of those ties has taken a back seat to the Obama campaign's efforts to win the Hispanic vote and his ability to rouse young and black voters. In spite of the drawn-out primary season, many voters have heard little about Obama's years in Jakarta — he lived there between 1967 and 1971, while his mother was married to Soetoro-Ng's father, an Indonesian businessman — or about his years in Hawaii, where Asian-Americans are a majority.

Soetoro-Ng, who lives in Honolulu, and Obama have different fathers and the same mother. Her father is Indonesian, his is Kenyan. Her husband is Chinese-Canadian.

Initially, as the campaign focused on fighting out the primaries, state by state, "the idea was to downplay to some degree race and ethnicity," said Soetoro-Ng in an interview with The Associated Press. "A lot of the emphasis had been on reaching out, making connections, closing the gaps."

That theme resonated among Obama supporters of all backgrounds, said Soetoro-Ng, who is nine years younger than Obama and considers him "the strong male force" in her life after her parents' divorce.

It was with Obama she attended her first blues concert and her first voter registration drive, she said. The two remain close: She was there when Obama's oldest daughter, Malia, 9, was born, and plans to help celebrate her 10th birthday on the 4th of July, on the campaign trail.

Soetoro-Ng's appearances give voters a chance to get to know Obama as a person, not just an elected official. Her stories illustrate the development of his character, from his days as a teenager who loved basketball and bodysurfing and didn't always get the strongest grades, to his growing sense of civic duty in the summers she spent with him in Chicago.

But she also has a political role to play. She plans to spend her summer vacation — she is a teacher at an all-girls' school in Hawaii — introducing her brother to crowds such as this one.

"We are ready for a more complex construction of identity as a country," she said, dismissing the possibility some voters might find it hard to relate to Obama's multiethnic background and foreign experience.

"Maybe not everybody is as mixed or as hybrid as he is. But he gets Kansas, because we have Kansas," she said, referring to their mother's background. "He gets the Midwest. He gets the south side of Chicago."

And he "has a lot of affection for Asian cultures, in all of their various forms," she said.

That cultural variety is among the reasons Asian-American and Pacific Islander voters have gotten less attention than other ethnic groups from the media — or even from the Obama campaign — during the primary season.

Asian-American voters represent about 5 percent of the population, or about 15.4 million people, but their communities are scattered around the country and harbor deep cultural and geopolitical differences that bleed into their voting behavior and ensure that many remain independent, harder to court.

"I'm not surprised we haven't had as much attention as Latinos and African-Americans," said Kamisugi. "We're underdeveloped and under-recognized" as voters.

In 2004, 56 percent of Asian-Americans voted for Democrat John Kerry and 44 percent for President Bush, according to exit poll data.

"It's not an easily definable vote," said Tony Quinn, a California political analyst. "You can't talk about it as a voting bloc — it's not."

Asians make up one-fourth of the foreign-born population in the United States; many are first-generation immigrants. That presents a challenge to politicians, said Gautam Dutta, executive director of the Asian American Action Fund,a political action committee whose goal is to increase Asian-American political participation.

"You can't have a one-size-fits-all approach," Dutta said.

This may explain why an event billed as the community's first National Presidential Town Hall, which drew about 2,000 Asian-American and Pacific Islander leaders, elected officials and voters in May got less attention from candidates who appeared and spoke before Hispanic and black civic organizations.

Hillary Rodham Clinton made a video appearance, Obama took questions over the phone. There was no response from Republican John McCain's campaign.

But some analysts argue that because Asian-Americans are just emerging as a political community engaging them now will pay off.

Census numbers show their growing importance. The Asian-American population grew 3 percent between 2004 and 2005 — more than another other group. And the Census projects the population will grow 213 percent by 2050, to 33.4 million.

In some key states, their weight is already considerable. Besides Hawaii, where Asian-Americans are 57.5 percent of the population, and California, where they're 13.5 percent, Asians are 7.7 percent of New Jersey and Washington, and 7.2 percent of New York.

In some races, even a comparatively small group can cast the key votes. In Virginia's 2006 Senate contest, Republican George Allen referred to an Indian-American as a "macaca" and the resulting outrage among Asians helped propel Democrat Jim Webb's come-from-behind victory. Webb won by 7,231 votes.

"Parties are hesitant to invest in communities where party loyalty is not fixed," said David Lee, who teaches political science at San Francisco State University, and heads the Chinese-American Voters Education Committee. "But if you don't spend the money, if you don't invest in Asian voters, why should they be loyal?"

Soetoro-Ng, and her husband, Konrad Ng, a professor at the University of Hawaii, are already doing some of that work.

Ng blogs on the Obama campaign's Web site, and Soetoro-Ng plans to continue to take time from her teaching throughout the fall to make phone calls to house parties, appear on radio broadcasts and perform other outreach for her brother.

"My brother is very interested in reaching out to communities," including Asian-Americans and Pacific Islanders, she said. "You're going to see a lot of new reaching out. It will be more deliberate."