MOUNT RUSHMORE NATIONAL MEMORIAL, S.D. – In a fiery speech to a mostly maskless crowd at Mount Rushmore on Friday night, President Donald Trump accused protesters of waging “a merciless campaign to wipe out our history” amid demonstrations against racial injustice and police brutality.

The sharp rebuke in a holiday address to mark the nation’s independence follows weeks of protests across the nation. Some demonstrators have destroyed or damaged Confederate monuments and statues honoring those who have benefited from slavery.

“This movement is openly attacking the legacies of every person on Mount Rushmore,” Trump said, adding that some on the political left hope to “defame our heroes, erase our values, and indoctrinate our children.”

His speech, intended to rev up his conservative base, comes as Trump has seen his standings slump over his handling of the pandemic and response to protests and unrest around the country. With four months until the election, Trump’s hopes for a second term — once buoyed by low unemployment and a roaring stock market — seem uncertain.

Amid the headwinds, Trump has sharpened his focus on his most ardent base of supporters as concern grows inside his campaign that his poll numbers in the battleground states that will decide the 2020 election are slipping.

Trump in recent weeks has increasingly lashed out at “left-wing mobs,” used a racist epithet to refer to the coronavirus and visited the nation’s southern border to spotlight progress on his 2016 campaign promise to build a U.S.-Mexico border wall.

The South Dakota event, while not a campaign rally, had the feel of one as the friendly crowd greeted Trump with chants of “Four more years!” and cheered enthusiastically as he and First Lady Melania Trump took the stage.

“Those who seek to erase our heritage want Americans to forget our pride and our great dignity, so that we can no longer understand ourselves or America’s destiny,” Trump said.

The event drew thousands of spectators, most of them without protective face masks, even as coronavirus cases spike across the country. The president was set to speak before a big fireworks show, the first to be held at the site in over a decade.

Hours before Trump arrived, protesters blocked a road leading to the monument. Authorities worked to move the demonstrators, mostly Native Americans protesting that South Dakota’s Black Hills were taken from the Lakota people against treaty agreements. About 15 protesters were arrested after missing a police-imposed deadline to leave.

Trump was expecting a South Dakota show of support, with the state Republican Party selling T-shirts that feature Trump on the memorial alongside George Washington, Thomas Jefferson, Theodore Roosevelt and Abraham Lincoln. But concern about the corona­virus risk and wildfire danger from the fireworks, along with the Native American groups’ protests, were also present.

GOP Gov. Kristi Noem, a Trump ally, had said social distancing wouldn’t be required and masks would be optional.

Noem, in her own remarks, echoed Trump’s attacks against his opponents who “are trying to wipe away the lessons of history.”

“Make no mistake: This is being done deliberately to discredit America’s founding principles by discrediting the individuals who formed them,” she said.

The small town of Keystone, which lies a couple of miles from the monument, was buzzing with people Friday hoping to catch a glimpse of the fireworks and the president. Many wore pro-Trump T-shirts and hats. Few wore masks.

“This is going to rank up in the top Fourth of Julys that I talk about,” said Mike Stewhr, who brought his family from Nebraska.

Mike Harris of Rapid City, who said he was a Republican, wore a mask and waved an anti-Trump flag. He also was sporting a handgun on each hip. He said he was worried the event would spark a virus outbreak.

“I think it’s a bad example being set by our president and our governor,” Harris said.

Leaders of several Indian tribes raised concerns that the event could lead to virus outbreaks among their members, who they say are particularly vulnerable to COVID-19 because of an underfunded health care system and a high incidence of chronic health conditions.

“The president is putting our tribal members at risk to stage a photo op at one of our most sacred sites,” said Harold Frazier, chairman of the Cheyenne River Sioux Tribe.

Some Native American groups used Trump’s visit to protest the Mount Rushmore memorial itself, pointing out that the Black Hills were taken from the Lakota people.

More than 100 protesters, many Lakota, lined the road leading from Keystone to the monument holding signs and playing Lakota music in 95-degree heat. Some held their fists in the air as cars loaded with event attendees passed by. Others held signs that read “Protect SoDak’s First People,” “You Are On Stolen Land” and “Dismantle White Supremacy.”

“The president needs to open his eyes. We’re people, too, and it was our land first,” said Hehakaho Waste, a spiritual elder with the Oglala Sioux tribe.

Several people who once oversaw fire danger at the national memorial have said setting off fireworks over the forest was a bad idea that could lead to a large wildfire. Fireworks were called off after 2009 because a mountain pine beetle infestation increased the fire risks.

Noem pushed to get the fireworks resumed soon after she was elected, even enlisting Trump’s help. The president brushed aside fire concerns earlier this year, saying, “What can burn? It’s stone.”

Trump has presided over several large-crowd events — in Tulsa, Okla., and at an Arizona megachurch — even as health officials warn against large gatherings and recommend face masks and social distancing.

The president plans a July 4th celebration on the National Mall despite health concerns from D.C. Mayor Muriel Bowser.

Also Friday, the Trump campaign got late word that Kimberly Guilfoyle, the girlfriend of the president’s oldest son, Don Jr., has contracted the coronavirus.

Sergio Gor, the chief of staff to the Trump campaign’s finance committee, said Guilfoyle was immediately isolated after the positive result to limit exposure. Gor says Donald Trump Jr. tested negative but is self-isolating as a precaution. He is also canceling his public events.