Former U.S. Ambassador to the United Nations (U.N.) Samantha Power Samantha Jane PowerSupport swells for renaming Edmund Pettus Bridge in Selma to honor John Lewis after his death 'Obamagate' backfires: Documents show Biden, Obama acted properly 'Unmaskings' may be common — and that's the problem MORE said Saturday that Sen. John McCain John Sidney McCainCindy McCain endorses Biden: He's only candidate 'who stands up for our values' Biden says Cindy McCain will endorse him Biden's six best bets in 2016 Trump states MORE's (R-Ariz.) funeral filled her with "optimism & determination" for the future of the country.

In a tweet Saturday, Power wrote that the values championed by McCain, who died last week at age 81 from brain cancer, are "indomitable and enduring."

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"Just leaving DC after #McCainsFuneral and am filled with optimism & determination. These last months have been dark, but McCain never gave up & faced far worse," the Obama-era U.N. official wrote Saturday.

"The values he championed - enshrined in the grand American anthems sung for him today - are indomitable and enduring," she continued.

Just leaving DC after #McCainsFuneral and am filled with optimism & determination. These last months have been dark, but McCain never gave up & faced far worse. The values he championed - enshrined in the grand American anthems sung for him today - are indomitable and enduring. — Samantha Power (@SamanthaJPower) September 1, 2018

The Washington, D.C., funeral was attended by top members across the political spectrum, many of whom were colleagues and friends of McCain throughout his more than 30 years serving as an Arizona senator.

Power's former boss was one of two former presidents to speak Saturday at McCain's funeral. President Trump Donald John TrumpOmar fires back at Trump over rally remarks: 'This is my country' Pelosi: Trump hurrying to fill SCOTUS seat so he can repeal ObamaCare Trump mocks Biden appearance, mask use ahead of first debate MORE was not invited to attend the service.

During his remarks, Obama appeared to rebuke "bombast" and politics of "phony controversies" in the current political climate.

"So much of our politics, public life, public discourse can seem small and mean and petty, trafficking in bombast, and insult, and phony controversies, and manufactured outrage," Obama told the crowd at the Washington National Cathedral.

"It's the politics that pretends to be brave and tough but in fact is born of fear," he added. "John called on us to be bigger than that. He called on us to be better than that."

McCain's daughter Meghan McCain explicitly took aim at the president's rhetoric in her eulogy.

"America does not boast because she does not have need to. The America of John McCain has no need to be made great again, because America was always great," McCain said to applause.

Trump spent Saturday at his Virginia golf course after issuing several tweets in the morning attacking the FBI and Justice Department, as well as trade difficulties with Canada.