Elon Musk joined Donald Trump onstage during a rally in Pennsylvania.

Musk said that voter turnout in support of Trump is paramount, or "this will be the last election."

The event took place at the same location where a gunman nearly assassinated Trump in July.

Donald Trump has a new headliner: Elon Musk.

The billionaire owner of some of the world's most prominent companies spoke at the former president's high-profile rally in Butler, Pennsylvania — the same place Trump was nearly assassinated in July.

Taking the stage alongside Trump, Musk leaped into the air several times and pumped his fist while wearing an all-black "Make America Great Again" hat and his signature "Occupy Mars" shirt.

"As you can see, I'm not just MAGA — I'm dark MAGA," Musk quipped.

He then compared Trump with President Joe Biden, saying that Biden "couldn't climb a flight of stairs" while Trump "was fist pumping after getting shot," referring to the July assassination attempt that left the former president wounded in the ear.

"So who do you want representing America?" Musk asked, garnering applause and chants of Trump's name.

In his brief appearance, Musk warned that voter turnout supporting the former president is paramount this year, or "this will be the last election." He said "the other side" wants to take away freedom of speech, take away the right to bear arms, and "take away your right to vote, effectively."

"President Trump must win to preserve the Constitution," Musk said during his remarks. "He must win to preserve democracy in America."

Musk and representatives for the Trump campaign did not immediately respond to requests for comment from Business Insider.

In a press release from the Trump campaign released before the event, Musk was listed as an attendee just after Trump's immediate family but before his running mate, JD Vance, in an apparent nod to how important the campaign views Musk's presence at the event.

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The rally took place at the same location, the Butler Farm Show Grounds, where on July 13, a gunman managed to graze Trump in the ear in what was easily the most dramatic moment of a historic presidential campaign season.

Immediately after the shooting, Musk officially endorsed Trump. He has been a vocal supporter since, mostly through posts on X, applauding the former president and critiquing his Democratic opponent, Vice President Kamala Harris, on a nearly daily basis.

But Musk and Trump haven't always been so chummy. In 2015, Musk said it would be "a bit embarrassing" if Trump secured the Republican presidential nomination. And in 2016, he said Trump was "not the right guy" for the presidency. As president-elect in late 2016, Trump announced Musk would join his economic advisory board, but Musk would later cut ties with the administration over disagreements on climate change policies.

The two found some common ground in 2020 while opposing COVID-19 regulations, but their feud intensified in July of 2022. At a Trump rally, Trump called Musk a "bullshit artist," after which Musk suggested Trump should not run for president again. Trump retaliated, saying Musk would be "worthless" without government subsidies and that Trump previously could have made Musk beg on his knees for government support.

Despite their on-again-off-again relationship, Musk has been fairly consistent in supporting Republican causes. Musk donated millions to conservative campaigns over the years, including at least $10 million to Florida Gov. Ron DeSantis, who competed against Trump for the GOP nomination. Musk endorsed DeSantis and interviewed him live on X as he launched his campaign, though the launch was riddled with glitches and mocked by Trump ruthlessly.

The relationship between the two has now completely changed. Musk is now one of the president's most prominent supporters. Musk has funded a pro-Trump super PAC, which has donated millions to Republican races and launched ads touting Trump as the only option to "save America."