Donald Trump attends a rally at the site of the July assassination attempt against him, in Butler, Pennsylvania, on Saturday. Reuters

The former president and Republican nominee picked up where he left off in July when a gunman’s bullet struck his ear. He began his speech with, "As I was saying,” and gestured toward an immigration chart he was looking at when the gunfire began.

"Twelve weeks ago, we all took a bullet for America,” Trump said. "All we are all asking is that everyone goes out and votes. We got to win. We can’t let this happen to our country.”

The Trump campaign worked to maximise the event’s headline-grabbing potential with just 30 days to go and voting already underway in some states in his race against his Democratic opponent, Vice President Kamala Harris. Musician Lee Greenwood appeared on stage and serenaded him with "God Bless the USA,” frequently played at his rallies, and billionaire Elon Musk spoke for the first time at a Trump rally.

"We fought together. We have endured together. We have pushed onward together,” Trump said. "And right here in Pennsylvania, we have bled together. We’ve bled.”

At the beginning of the rally, Trump asked for a moment of silence to honour firefighter Corey Comperatore, who died as he shielded family members from gunfire in July. Classical singer Christopher Macchio sang "Ave Maria” after a bell rung at the same time that gunfire began on July 13. Several of Comperatore's family members were in attendance, including his widow, Helen, who stood during Trump's remarks next to the former president's daughter-in-law, Lara Trump.

Standing behind protective glass that now encases the stage at his outdoor rallies, Trump called the would-be assassin "a vicious monster” and said he did not succeed "by the hand of providence and the grace of God.” There was a very visible heightened security presence, with armed law enforcers in camouflage uniforms on roofs.

Trump honoured Comperatore and recognised the two other July rallygoers injured, David Dutch and James Copenhaver. They and Trump were struck when 20-year-old shooter Thomas Matthew Crooks of Bethel Park, Pennsylvania, opened fire from an unsecured rooftop nearby before he was fatally shot by sharpshooters.

The building from which Crooks fired was completely obscured by tractor-trailers, a large grassy perimeter and a fence.

How Crooks managed to outmaneuver law enforcement that day and scramble on top of a building within easy shooting distance of the ex-president is among many questions that remain unanswered about the worst Secret Service security failure in decades. Another is his motive.

Trump lost Pennsylvania four years ago after flipping it to the Republican column in 2016. He needs to drive up voter turnout in conservative strongholds like Butler County, an overwhelmingly white, rural-suburban community, if he wants to win Pennsylvania in November after losing it four years ago. Harris, too, has targeted her campaign efforts at Pennsylvania, rallying there repeatedly as part of her aggressive outreach in critical swing states.

"Pennsylvania, clearly, is going to be the center of the universe for the next 30 days, for both sides, and we’re pretty bullish on where we are here organizationally, politically, and in terms of the resources that we’ve been able to commit here,” campaign senior adviser Chris LaCivita told reporters.

Associated Press