WASHINGTON (AP) - President Donald Trump celebrated "the greatest political journey in human history" Thursday in a Fourth of July commemoration before a soggy, cheering crowd of spectators, many of them invited, on the grounds of the Lincoln Memorial. Supporters welcomed his tribute to the U.S. military while protesters assailed him for putting himself center stage on a holiday devoted to unity.

Trump called on Americans to "stay true to our cause" in a program that adhered to patriotic themes and hailed an eclectic mix of history's heroes, from the armed forces, space, civil rights and other endeavors of American life.

He largely stuck to his script, avoiding diversions into his agenda or re-election campaign. But in one exception, he vowed, "Very soon, we will plant the American flag on Mars," actually a distant goal not likely to be achieved until late in the 2020s if even then.

A late afternoon downpour drenched the capital's Independence Day crowds and presaged an evening of possible on-and-off storms. But Trump's speech unfolded in occasional rain, and the warplanes and presidential aircraft he had summoned conducted their flyovers as planned, capped by the Navy Blue Angels aerobatics team.

By adding his own, one-hour "Salute to America" production to capital festivities that typically draw hundreds of thousands anyway, Trump became the first president in nearly seven decades to address a crowd at the National Mall on Independence Day.

Protesters objecting to what they saw as his co-opting of the holiday inflated a roly-poly balloon depicting Trump as an angry, diaper-clad baby.

Trump set aside a historic piece of real estate - a stretch of the Mall from the Lincoln Monument to the midpoint of the reflecting pool - for a mix of invited military members, Republican and Trump campaign donors and other bigwigs. It's where Martin Luther King Jr. gave his "I have a dream" speech, Barack Obama and Trump held inaugural concerts and protesters swarmed into the water when supporters of Richard Nixon put on a July 4, 1970, celebration, with the president sending taped remarks from California.

Aides to the crowd-obsessed Trump fretted about the prospect of empty seats at his event, said a person familiar with the planning who was not authorized to be identified. Aides scrambled in recent days to distribute tickets and mobilize the Trump and GOP social media accounts to encourage participation for an event hastily arranged and surrounded with confusion.

Many who filed into the sprawling VIP section said they got their free tickets from members of Congress or from friends or neighbors who couldn't use theirs. Outside that zone, a diverse mix of visitors, locals, veterans, tour groups, immigrant families and more milled about, some drawn by Trump, some by curiosity, some by the holiday's regular activities along the Mall.

Protesters earlier made their voices heard in sweltering heat by the Washington Monument, along the traditional parade route and elsewhere, while the VIP section at the reflecting pool served as something of a buffer for Trump's event.

In the shadow of the Washington Monument hours before Trump's speech, the anti-war organization Codepink erected a 20-foot tall "Trump baby" balloon to protest what activists saw as his intrusion in Independence Day and a focus on military might that they associate with martial regimes.

"We think that he is making this about himself and it's really a campaign rally," said Medea Benjamin, the organization's co-director. "We think that he's a big baby. ... He's erratic, he's prone to tantrums, he doesn't understand the consequences of his actions. And so this is a great symbol of how we feel about our president."

The balloon remained tied down at the Mall because park officials restricted the group's permission to move it or fill it with helium, Benjamin said.

Protesters also handed out small Trump-baby balloons on sticks. Molly King of La Porte, Indiana, a 13-year-old Trump supporter in sunglasses and a "Make America Great Again" hat, happily came away with one.

"They're making a big stink about it but it's actually pretty cute," she said. "I mean, why not love your president as you'd love a baby?"

A small crowd gathered to take pictures with the big balloon, which drew Trump supporters and detractors.

"Even though everybody has different opinions," said Kevin Malton, a Trump supporter from Middlesboro, Kentucky, "everybody's getting along."

But Daniela Guray, a 19-year-old from Chicago who held a "Dump Trump" sign, said she was subjected to a racial epithet while walking along the Constitution Avenue parade route and told to go home.

She said she did not come to the Mall to protest but ended up doing so. "I started seeing all the tanks with all the protests and that's when I said, 'Wait, this is not an actual Fourth of July,'" she said. "Trump is making it his day rather than the Fourth of July."

Trump had sounded a defensive note Wednesday, tweeting that the cost "will be very little compared to what it is worth."

"We own the planes, we have the pilots, the airport is right next door (Andrews), all we need is the fuel," he said, referring to Maryland's Joint Base Andrews, home for some of the planes expected for the holiday flyover. "We own the tanks and all. Fireworks are donated by two of the greats."

Trump glossed over the expense of shipping tanks and fighting vehicles to Washington by rail and guarding them for several days, and other costs.

Not since 1951, when President Harry Truman spoke before a large gathering on the Washington Monument grounds to mark the 175th anniversary of the signing of the Declaration of Independence, has a commander in chief made an Independence Day speech to a sizable crowd on the Mall.

Pete Buttigieg, one of the Democrats running for president, said: "this business of diverting money and military assets to use them as a kind of prop, to prop up a presidential ego, is not reflecting well on our country." Buttigieg, the mayor of South Bend, Indiana, is a Navy Reserve veteran who served in Afghanistan in 2014.

Two groups, the National Parks Conservation Foundation and Democracy Forward, want the Interior Department's internal watchdog to investigate what they say may be a "potentially unlawful decision to divert" national parks money to Trump's "spectacle."

Trump and the event's organizers could be on the hook to reimburse the government millions of dollars if he goes into campaign mode, in violation of federal appropriations law and the Hatch Act, which bars politicking on government time, said Walter Shaub, who left the Office of Government Ethics in 2017 after clashing with the White House over ethics and disclosure issues.

Washington has held an Independence Day celebration for decades, featuring a parade along Constitution Avenue, a concert on the Capitol lawn with music by the National Symphony Orchestra and fireworks beginning at dusk near the Washington Monument.

Trump altered the lineup by adding his speech, moving the fireworks closer to the Lincoln Memorial and summoning the tanks and warplanes.

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