Donald Trump launched a full-throated attack on Democratic rivals Joe Biden and Kamala Harris in Grand Rapids, Michigan, on Saturday as he returned to the campaign trail a week after surviving an assassination attempt in Butler, Pennsylvania.

In his first rally since the shocking shooting, and his first with new running mate Ohio senator JD Vance, Trump appeared on stage with the conspicuous white ear bandage he wore during the Republican national convention replaced by a smaller covering. He referred to the assassination attempt as a “horrific event” and said he stood before supporters “by the grace of God. I shouldn’t be here, but let’s face it, something very special happened.”

Trump said “he owed his life to immigration”, because he’d turned his head to the right toward a chart about border crossings fractionally before the bullet whizzed past his head, grazing his ear. “I hope I never have to go through that again,” Trump added. He said his opponents call him “a threat to democracy” but countered that he “took a bullet for democracy”.

Trump also referred to leadership chaos within the Democratic party, which has been consumed with a debate over whether Joe Biden should step down from his re-election bid amid concerns about his age and mental acuity. “They have no idea who their candidate is, and neither do we,” Trump jibed. He called Biden a “feeble old guy”.

Trump, appearing jocular and in good spirits during a lengthy speech, said he would rather be in Michigan than sitting “on some boring beach watching the waves coming in” – another dig at Biden, who is currently recovering from Covid at his Delaware beach home.

The former US president went on to predict a landslide election, asking the crowd whether they preferred he run against Vice-President Kamala Harris, to loud boos, or Biden, to cheers. But he said he would also also be happy to run against Michigan governor Gretchen Whitmer who, he said, has done “a terrible job”.

Trump hit his usual themes, attacking electric vehicles, China and trade and promising a massive effort on deportation. He talked in his usual extreme rhetoric, especially when it came to immigration, where he talked in dire terms of crimes committed by immigrants that echo rightwing conspiracy theories.

But Trump also pushed back on accusations that a second Trump presidency would be influenced by the extremist manifesto Project 2025 from the conservative Heritage Foundation and including scores of people close to Trump and his campaign.

The document, he said, had been produced by the “severe right – very, very conservative and the opposite of the radical left. I don’t know anything about it, and I don’t want to know anything about it.”

Trump was preceded on the stage by Vance, who received a warm reception, despite the sports rivalry between his home state of Ohio and Michigan.

Vance criticized both Republicans and Democrats in his speech for previously failing to protect manufacturing jobs in Michigan and the US. “Both parties were broken in very profound ways until Trump came along,” he said.

Crowds numbering in the thousands waited outside the 12,000-capacity Van Andel Arena in Grand Rapids, Michigan, to greet the former president amid what was expected to be improved security after the Secret Service and local police allowed 20-year-old would-be assassin Thomas Matthew Crooks to get on a roof with sightline of the stage in Butler, Pennsylvania, and fire several shots at the former president.

Grand Rapids law enforcement declined to say whether it had deployed extra officers, referring questions to the presidential security agency. But, unlike the open county fair fairgrounds last week, Trump’s rally on Saturday was in an enclosed arena where security would be easier to secure and without, as in Butler, outer areas that were assigned to local police.

“I think what you’re going to see is just a visual increase of additional agents and certainly some pretty unprecedented level of police officers just because it’s the first event after the previous Saturday,” former Secret Service agent Jason Russell told Michigan Live.

Eric Winstrom, the Grand Rapids police chief, said his department had worked closely with federal partners on planning for the event “with solid operational planning, effective resource deployment, and an unwavering commitment to the safety of the community we serve”.

John Schaut, chair of the Republican party chapter in Kent, Michigan, told Michigan Live the shooting hadn’t deterred Trump fans and predicted “a blowout event”.

Trump’s campaign released an official update on his injuries on Saturday. Texas Representative Ronny Jackson, who served as Trump’s White House physician, said Saturday that the bullet fired from Crooks’ gun came “less than a quarter of an inch from entering his head, and struck the top of his right ear” and produced a “2cm wide wound”.

Jackson said the wound is healing but that the former president is still experiencing some bleeding, requiring an ear dressing. “Given the broad and blunt nature of the wound itself, no sutures were required,” he wrote.

Michigan is one of a handful of must-win states for Trump and Biden. Recent polling averages place Trump with a 4% lead over Biden, at 46% to 42%. That tallies with the pattern in other key battleground states, especially in the wake of the disastrous debate performance by Biden three weeks ago that triggered a wave of panic in the party about this electability. On a national level, Trump has opened a lead against Biden in head-to-head surveys.

According to local news reports, supporters began arriving for the rally as early as Friday afternoon, and by midday Saturday, lines to get in to see Trump stretched six blocks.

“I think it’s amazing. It just shows how strong he is and we’re so very proud of him, not that we would expect anybody, if they weren’t up to it, to be here like this,” supporter Julie Bryant of Marshall, Michigan, told Michigan Live. “We’re just here to support, especially after what he’s just been through.”

Supporter Adam Salton said he’d been in line since 6am: “Screw the right and the left, this is about Trump, this is about us. He could be on a golf course right now, he could be with his family, but he’s out here doing this for us so I’ll stand out here for eight hours for him, because it’s for us.”