Republican presidential candidate Donald Trump has returned to the rural Pennsylvania site where he was nearly assassinated, rallying a large crowd in the critical battleground state a month before the US election.

“As I was saying,” Trump said as he appeared on stage, pretending he was resuming the speech that was interrupted when he was grazed in the ear by a bullet on July 13.

In mid-speech Trump called up on stage a powerful ally, Elon Musk, CEO of Tesla and owner of social media platform X. It was Musk’s first time at a Trump campaign event since he endorsed the former president after July 13.

He literally jumped up on stage with his arms held high.

“The true test of someone’s character is how they behave under fire,” Musk said, calling the election a “must-win situation” for Trump and urging the crowd to register to vote.

“Be a pest to everyone you know,” Musk said.

Trump saluted firefighter Corey Comperatore, who was shot and killed by the shooter in July. Two other people who were wounded.

At 6.11pm, the exact time when gunfire erupted on July 13, Trump called for a moment of silence. A bell then tolled four times, once for each of the four victims, including Trump.

In his speech, Trump hinted darkly without evidence about facing “an enemy from within” more dangerous than a foreign adversary.

Of the gunman, he said “a cold-blooded assassin aimed to silence me” but “did not stop our movement.”

The crowd appeared to be in the tens of thousands, many wearing Trump regalia. Some chanted the “fight, fight, fight” slogan Trump used to rally his followers moments after he was shot.

“We’re here to say ‘we can’t be intimidated, we can’t be stopped’,” Ohio Republican Senator JD Vance, Trump’s vice-presidential running mate, told the crowd.

He rejected the argument from Vice President Kamala Harris and other Democrats that Trump represents a threat to democracy.

“Donald Trump took a bullet for democracy. What the hell have you done?” he said.

People cheered when Trump’s plane did a flyby over the rally prior to landing as the loudspeakers played the Top Gun movie theme song.

Republican officials hoped Trump’s return to Butler would drive up turnout for him among hard-core supporters in Pennsylvania, a state he and Harris see as crucial to winning on November 5.

“I’m going back to Butler because I feel I have an obligation to go back to Butler,” Trump told the NewsNation cable news network earlier last week.

“We never finished what we were supposed to do.”

Introductory speakers at the rally focused on remembering Comperatore, whose family members were in the crowd.

“We will not let that tragic day overshadow our community’s light,” said JD Longo, mayor of the nearby town of Slippery Rock.

The Butler shooting led to widespread criticism of the Secret Service and the resignation of its director.

A Secret Service probe found communication gaps and a lack of diligence ahead of the shooting. In its aftermath, the agency approved extra security measures for Trump, including using bulletproof glass to shield him at outdoor rallies.

Secret Service spokesperson Anthony Guglielmi said before Saturday’s rally that there had been “comprehensive changes and enhancements to our communications capabilities, resourcing and protective operations”.

Trump credits turning his head to read a chart on a big video as having saved his life. A vivid image from the moments after is him raising his fist and shouting “fight” to his supporters, while blood drips down his face.

“I love that chart,” Trump said when it flashed on screen.

“Isn’t it beautiful?”

-with Reuters