NORMAN, Oklahoma — President Joe Biden on Friday, during his first visit to Native Country, formally apologized to Native Americans for the “sin” of the government-run boarding school system that forcibly separated Indian children from their parents for decades, calling it a “stain on American history.”

“This is a sin committed on our souls,” Biden said in his voice full of anger and emotion. “Frankly, there is no excuse for this apology taking 50 years.”

While talking about the abuse and deaths suffered by indigenous children due to the policies of the federal government, Biden noted that the shameful history is unknown and must be told. The president described how his policies sought to support Native Americans with jobs and new infrastructure.

Democrats hope Biden’s visit to the Gila River Indian Community land on the outskirts of metro Phoenix, Arizona, will also provide a boost to Vice President Kamala Harris’ engagement efforts in a key battleground state.

Biden, whose presidency is over, promised tribal leaders nearly two years ago that he would visit Indian Country.

Apologizing for the U.S. government’s role in the abuse and neglect of Native children is “something that should have been done a long time ago,” the president said in a call with reporters Thursday before leaving for Arizona. For decades, federal boarding schools were used to assimilate children into white society, according to the White House.

The moment will also give Biden and Harris a chance to highlight his support for tribal nations, a group that has historically supported Democrats, in a state he won by just 10,000 votes in 2020.

The race between Harris and former President Donald Trump is expected to be similarly close, and both campaigns are doing what they can to increase turnout from core supporters.

“The race has now become a turnout grab,” said Mike O’Neil, a nonpartisan pollster based in Arizona. “The overall trend lines have been extremely stable. The question is which candidate can turn away voters in a race that looks set to be decided by narrow margins.”

It has been used sparingly by Harris and other Democrats on the campaign trail since Biden ended his reelection campaign in July.

But analysts say Biden could help Harris appeal to Native American voters, a group that lags others in turnout rates.

In 2020, some tribal lands in Arizona saw a surge in voter turnout as Biden defeated Trump and became the first Democratic presidential candidate to win the state since Bill Clinton in 1996.

Biden is visiting in his official capacity, and a formal apology that tribes have long sought is likely to attract the attention of Native Americans across the country.

At least 973 Native American children died in the U.S. government’s abusive boarding school system during a 150-year period that ended in 1969, according to an Interior Department investigation that called for an apology from the U.S. government.

At least 18,000 children, some as young as 4, were taken from their parents and forced to attend schools that attempted to assimilate them.

“President Biden deserves credit for finally bringing attention to the issue and other issues affecting the community,” said Ramona Charette Klein, 77, a residential school survivor and an enrolled member of the Chippewa Turtle Mountain Band. “I think this will reflect well on Vice President Harris, and I hope that momentum continues.”

He added that whoever is the next president must take concrete steps and begin to undo the devastation that residential schools have wrought on tribes.

Democrats have stepped up aid efforts to Native American communities.

Both Harris and her running mate, Minnesota Gov. Tim Walz, met with tribal leaders in Arizona and Nevada this month. Clinton, who serves as Harris’ surrogate, also met with the head of the Lumbee Tribe in North Carolina last week.

The Democratic National Committee recently launched a six-figure advertising campaign targeting Native American voters in Arizona, North Carolina, Montana and Alaska through digital, print and radio ads.

Democratic Rep. Ruben Gallego, locked in a competitive race with Republican Kari Lake for Arizona’s open Senate seat, visited all 22 of Arizona’s federally recognized tribes.

Harris recently kicked off a campaign rally in Chandler, where the Gila River reservation is located, by addressing the tribal leader.

He also reminded the crowd that he was the first vice president to visit the region. She and her husband, Doug Emhoff, visited the community last year.

“I believe strongly that the relationship between tribal nations and the United States is sacred and that we must respect tribal sovereignty, embrace our trust in treaty obligations, and secure the right of tribes to self-determination,” Harris said.

The White House says Biden and Harris have had outstanding track record with Native Americans over the past four years.

He designated the sacred Avi Kwa Ame, a desert mountain in Nevada, and the Baaj Nwaavjo I’tah Kukveni-Footprints of the Ancestors of the Grand Canyon in Arizona as national monuments and restored the boundaries of Bears Ears National Monument in Utah.

In addition, the administration directed nearly $46 billion in federal spending to tribal nations. The money helped bring electricity to a region that had none, expand access to high-speed internet, improve water hygiene, build roads, and more.

Biden chose former New Mexico Rep. Deb Haaland, the first Native American appointed to a Cabinet position, as Interior secretary. Haaland is a member of Laguna Pueblo in New Mexico.

He also ordered a sweeping review of the federal government’s problematic legacy of residential school policies in June 2021, which led to Biden’s official apology.

“He made commitments to Indian Country and he fulfilled every single one of those commitments,” Haaland said.

Thom Reilly, co-director of the Center for Independent and Sustainable Democracy at Arizona State University, said both Harris and Trump’s campaigns and their allies have devoted a significant amount of effort to microtargeting in Arizona.

Reilly noted that Harris is also focused on reducing Trump’s advantage among the state’s Mormon voters (a group that has historically supported Republicans). Trump, meanwhile, has placed a particular focus on young men as the campaign seeks to narrow the Democratic advantage with young voters.

“They’re trying every way to see if they can get a few more votes here and there,” Reilly said. “The Indian community is one of the groups that Harris hopes will excel and help make a difference.”