Republican presidential candidate Donald Trump on Saturday returned to the rural Pennsylvania site where he was nearly assassinated, rallying a large crowd in the critical battleground state one month before the November 5 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 his first time at a Trump campaign event since he endorsed the former president after July 13.

Musk 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, and two other people who were wounded.

At 6:11 p.m., 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.

Vance 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?" Vance 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.

July 13 was the first of two attempts on Trump's life. On September 15, a gunman hid undetected for nearly 12 hours at Trump's golf course in West Palm Beach, Florida, with plans to kill him, prosecutors have said, but was thwarted by a U.S. Secret Service agent patrolling the course ahead of Trump.

Republican officials hope Trump's return to Butler will drive up turnout for him among hardcore supporters in Pennsylvania, a state he and his Democratic opponent, Kamala 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 this week. "We never finished what we were supposed to do."

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

Critics raised concerns about how the 20-year-old suspect, Thomas Matthew Crooks was able to access a nearby rooftop with a direct line of sight to where Trump was speaking. Crooks was subsequently shot to death by Secret Service agents.

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 in a statement 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. With blood dripping down his face, he raised a fist and shouted "fight" to his supporters, a vivid image from that day. He wore a white bandage on his wounded ear for days afterward.

"I love that chart," Trump said when it flashed on screen on Saturday. "Isn't it beautiful?"

(With input from Reuters)