WASHINGTON — At a July fundraiser in the elegant Mandarin Oriental hotel near Washington’s Tidal Basin, President Barack Obama met with some of his most steadfast supporters — two dozen political and business leaders eager to write sizable checks to help keep him in the White House.

All were leaders of Native American tribes, who pressed their issues with a president they say is attuned to their needs.

Bill John Baker, principal chief of the Cherokee Nation, told Obama his Oklahoma tribe is owed $50 million for its costs of administering federal health services.

“He said, ‘Let me look into this and see what we can do,’ ” Baker recalled. A week later, he received a letter from the White House pledging to follow up. A White House spokesman said the administration has been reaching out to many tribes on the same issue.

“President Obama is a promise keeper,” Baker said. “He promised that he would work with Indian country, that he would help us, and he has done that at every turn.”

The tribes have shown their gratitude, giving at least $2.5 million to Obama’s re-election campaign through the end of July — far outstripping their donations in other recent presidential elections, according to data provided by the nonpartisan Center for Responsive Politics.

Melvin R. Sheldon Jr., chairman of the Tulalip Tribes, which have donated more than $181,000 to the campaign, said he expects “another surge of giving between now and November.”

The Tulalip Tribes have received more than $10 million in stimulus funds, including $2.7 million for early childhood development services and $2 million to restore a fish passage for Chinook salmon on the lower Snohomish River.

Republican challenger Mitt Romney has just begun to make appeals to tribes, holding a fundraiser at his Boston headquarters last month. So far, he has raised about $750,000 from tribes, according to a campaign official.

The donations highlight a potentially lucrative and, until now, largely untapped source of funds for presidential politics. Unlike corporations and unions, tribes can give directly to candidates. And because of their status as sovereign nations, they can donate more to presidential campaigns than individuals, who cannot give more than $117,000 in federal donations every two years.

Tribes, primarily those engaged in the $26 billion Indian gambling industry, already have become major players in state and congressional politics. In California, for example, four tribes spent more than $100 million to pass a ballot measure allowing them to expand casinos in 2008.

Tribal leaders say Obama won their loyalty by doing more for Native Americans than any other president. Obama — dubbed Barack Black Eagle when he was adopted by the Crow Nation during the 2008 campaign — is the first president to hold an annual summit with leaders from the 566 federally recognized tribes.

The tribes received $3 billion as part of the 2009 economic stimulus package. In addition, the administration beefed up tribal law enforcement powers and improved Indian health care services.

Perhaps most significant, the administration has settled billions of dollars in outstanding land and trust claims, including a 13-year-old class action lawsuit originally brought by Elouise Cobell, a member of the Montana Blackfeet Nation, alleging that the federal government had cheated Native Americans out of income from land and mineral rights the government managed on their behalf for more than a century.

At one point, President George W. Bush’s administration offered a $7 billion deal to settle the Cobell case and more than 100 other tribal trust claims, as well as bar any future suits and relieve the government of its historic accounting obligations. Cobell rejected that as “an insult.” The Obama administration ultimately settled the Cobell case in December 2009 for $3.4 billion, and has committed another $2 billion to settle dozens of other long-standing claims by the tribes.

At a Native American caucus held during the Democratic National Convention in Charlotte, N.C., this month, administration officials reminded tribal leaders that Obama ended the contentious Cobell litigation.

“Barack Obama said he wanted it resolved and he wanted to do good things for Indian country to address the injustices that had happened,” said Interior Secretary Ken Salazar, whose department oversees most Indian affairs.

Until Obama’s election, “what the United States has done is essentially taken a position that Indian Country is something to almost be forgotten,” Salazar said. “Your president, Barack Obama, Black Eagle, has said that’s not going to be the case.

“He has your back, and so come this November, we need you to have his back.”

A key player who is both helping Obama’s re-election and representing tribes in claims against the government is Washington lawyer Keith Harper, who signed on early to the Obama campaign in the spring of 2007 and helped design a strategy to woo tribal leaders.

Harper, a member of the Cherokee Nation, helped organize the July fundraiser, as first reported in Indian Country Today, a Native American publication, as well as an earlier one in January. He served on the president’s 2008 transition team, has helped raise more than $500,000 for Obama’s re-election and co-hosted the Native American caucus at the convention.

At the same time, Harper has represented tribes in high-stakes dealings with the government. Several clients, including the Ak-Chin Indian Community and the Salt River Pima-Maricopa Indian Community, currently have cases against the government.

He was one of the lead lawyers in Cobell case and stands to share in $99 million in legal fees.

His work on Cobell presented a potential conflict in 2008, when he was advising the incoming administration. During the transition, Harper was originally assigned to oversee a review of the Interior Department, which was involved with the Cobell negotiations, with an understanding that he would not participate in discussions of the case. Within days, however, the Obama transition team — worried about a perception of a conflict of interest — changed his assignment to the National Indian Gaming Commission, according to people familiar with the situation.

Harper represents tribal clients with casinos. But he said he did not have any client matters before the gaming commission during his time on the transition team, or during the year before and after, following the campaign’s rules. And Harper said he recused himself whenever the Cobell case came up during the campaign.

“That means that I did not participate, directly or indirectly, in the discussion of Cobell,” he wrote in an email.

White House spokesman Eric Schultz said Harper complied with rules that required transition team members to meet the “highest ethical standards of conduct.”

Harper’s “important role in the Cobell case should not preclude him from playing a part in the political process on behalf of one candidate or another,” added Obama campaign spokeswoman Clo Ewing.

During the 2008 campaign, Obama met about a dozen times with tribes across the country, including a visit that May to the Crow Indian Reservation in Montana, where he was given a Crow name that translates as “One Who Helps People Throughout the Land.”

Cedric Black Eagle, the tribal chairman whose parents adopted Obama in a traditional ceremony, praised him for his efforts to honor old obligations to Indians. “I think that’s really important for us, as almost the forgotten people in this country,” he said.

At least 47 tribes have donated to Obama’s campaign or the Democratic National Committee in the last two years. Among them are some of the top Indian casino operators, including prominent California tribes, such as the Morongo Band of Mission Indians in Banning ($135,800) and the Pechanga Band of Luiseno Indians in Temecula ($126,600).

The Cherokee Nation received more than $10 million to repair highways and build housing, among other projects. Baker, the tribe’s chief, called the Recovery Act “a godsend.”

“We live and die in D.C.,” said Baker, whose iPhone has a picture of him with Obama. “There are so many programs in the past we’ve had to go hat in hand.”

There is much at stake for tribes in the coming four years: outstanding trust claims, efforts to expand tribal authority over domestic violence cases and regulation of online gambling.

At the Native American caucus in Charlotte, Harper urged a room crowded with tribal representatives to do everything possible to re-elect Obama if they wanted the “inclusion of Indian country in every policy consideration.”

White House counselor Pete Rouse, who referred to Harper as “my old friend Keith,” told the leaders that their support had been noticed.

“Believe me, you’re having an impact,” he said. “Certainly the president knows about it, the president’s people know about it.”

Richard A. Monette, former chairman of the Turtle Mountain Band of Chippewa Indians in North Dakota and an assistant professor at the University of Wisconsin Law School, has misgivings about the tribes’ increasing role in Washington politics.

He says tribal donations are mostly casino money in Indian dress, and he worries that playing big-money politics may end up damaging the tribes.

“They used to have a little bit of moral high ground because of the historical situation. They used to know who their friends were in D.C.,” said Monette, who formerly worked at the Senate Indian Affairs Committee and at the Bureau of Indian Affairs. “Now it’s the friends they bought and paid for, and when they stop paying, their friends are going to leave too.”

Tribal leaders say it’s silly to expect Native Americans to play by different rules from those of other interest groups.

Jacqueline Pata, executive director of the nonpartisan National Congress of American Indians, says some Indians, as members of sovereign nations, once shunned the idea of voting for president. Now, they realize that engaging in national politics — and writing checks to campaigns — is “important for keeping our voice at the table.”

“Whether we like it or not, it’s the way America runs,” Pata said, “and it’s the system that’s out there.”