• Tesla CEO Elon Musk has thrown his support behind former President Donald Trump in the 2024 election, but the two have a complicated history.
• Trump has called climate change a "hoax" and has long been a critic of electric cars.
• As recently as 2022, Musk and Trump were locked in an open feud, publicly slinging insults at each other on social media, political rallies and elsewhere.

NASHVILLE, Tenn. —  Former President Donald Trump's highly anticipated keynote address at the biggest bitcoin gathering of the year started over an hour late.

As the crowd of investors, enthusiasts and the crypto-curious grew increasingly antsy at the Bitcoin Conference in Nashville, Elon Musk's private jet was touching down 200 miles away in Memphis, Tennessee.

It was July 27, just two weeks after Trump had survived an assassination attempt in Pennsylvania. Hours later, he'd been publicly endorsed by the Tesla CEO for a second term.

Inside Nashville's Music City Center, rumors had been swirling all week that Musk would make a surprise appearance at the conference, and maybe even moderate a fireside chat with Trump.

Musk didn't show, but he was very much present.

"I love Elon. He's great," Trump told the crowd. "He endorsed me and great endorsement and everything else, but not everybody has to have an electric car."

Yet Trump's comments in Nashville were notably toned down from what he'd said about Musk just a week earlier at a rally in Michigan.

"I love Elon Musk ... we have to make life good for us smart people. And he's as smart as you get," Trump said at the time. "He gives me $45 million a month! C'mon. Not $45 million. He gives me $45 million a month."

He continued, "I mean other guys, they give you $2 and you got to take them to lunch, you got to wine 'em and dine 'em."

So what happened between July 20 in Michigan and July 27 in Nashville to tamp down Trump's gushing praise? The answer appears simple: On July 22, Musk denied the extent of the pledge.

"What's been reported in the media is simply not true," Musk told podcaster Jordan Peterson. "I'm not donating $45 million a month to Trump." In a July 25 post on X, the social media company he owns, Musk said he was making donations to a political action committee supporting Trump "but at a much lower level." 

The relationship between Musk, the world's wealthiest person, and Trump, the Republican nominee for president, is as volatile as the characters themselves. Over the years, they've made fun of each other, talked down to one another and taken opposite sides on key issues. But of late, they've emerged as parallel heroes to the far right, a group that includes a healthy dose of crypto enthusiasts, and are united in a single quest: defeating Democrats in 2024.

How far Musk is willing to go to financially support Trump in his campaign, now against Vice President Kamala Harris, is another matter. Musk set up a super PAC called America PAC days after endorsing Trump, but it's not clear how much money he's contributed, and the North Carolina Attorney General's Office said Monday that it's eyeing the group following a complaint that it's collecting personal data while failing in its promise to help users register to vote.

The Federal Election Commission website shows limited financial contributions from America PAC. Federal filings list total disbursements of $7.78 million from April 1 through June 30, mostly for two transactions: $3.87 million to "support" Trump and the same amount to "oppose" President Joe Biden.

Based on Trump's social media commentary, more about their relationship may be coming soon. Trump wrote in a post on Truth Social on Tuesday that the two will be speaking together publicly next week.

"ON MONDAY NIGHT I'LL BE DOING A MAJOR INTERVIEW WITH ELON MUSK — Details to follow!" Trump wrote.

Musk didn't respond to a request for comment for this story. Steven Cheung, communications director for the Trump presidential campaign, said in an email, "Stay tuned! Very exciting stuff!"

'I don't hate the man'

As recently as 2022, Musk and Trump were locked in an open feud, publicly slinging insults at each other on social media, at political rallies and elsewhere.

"I don't hate the man, but it's time for Trump to hang up his hat & sail into the sunset," Musk wrote in a 2022 social media post.

That same year, Trump called Musk a "bull---- artist," claiming the tech exec told him privately that he'd voted for him.

What had become clear was that Musk wasn't going to support a Biden reelection.

Musk said he'd voted for Biden in 2020, but the following year the president left Musk out of an EV summit at the White House, where he met with top executives from General Motors, Ford and Stellantis. Musk wrote in a tweet, "Yeah, seems odd that Tesla wasn't invited."

Biden is a pro-labor president, while Tesla is non-union and has run afoul of federal labor laws.

By 2022, Musk indicated he was leaning toward Ron DeSantis, Republican governor of Florida, as chatter about the 2024 election ramped up. DeSantis ended up launching his presidential campaign in a May 2023 livestream on X, which Musk owns. The stream with Musk and longtime friend David Sacks was a technical disaster, plagued by glitches. DeSantis' campaign fizzled and formally came to an end in January.

Two months later, Musk reportedly headed down to Trump's Mar-a-Lago resort in Florida, as Trump was trying to rally donor support. In an interview on CNBC's "Squawk Box" on March 11, Trump spoke positively about Musk, saying he's been "friendly with him over the years," had "helped him" when he was president, and that he "liked him."

"We obviously have opposing views on a minor subject called electric cars," Trump told CNBC's Joe Kernen. "I'm all for electric cars, but you have to have all of the alternatives," he said, adding that EVs "cost too much and they're all going to be made in China."

Whatever differences the two may have on EVs, they're increasingly aligned politically. Both have described Harris as a communist and are prone to lashing out at anything involving DEI — diversity, equity and inclusion. They're vocal in opposing transgender rights. Both have spread false reports about noncitizens voting in U.S. elections.

Former Ford CEO Mark Fields said it's not just about politics for Musk. Between his various companies —Tesla, aerospace and defense contractor SpaceX, social media company X and AI startup xAI — Musk has a lot of projects that could use assistance from the White House.

"The bottom line, a positive relationship with the president has a lot of benefits, not only potentially for Tesla, for things like autonomy or AI or robotics, but his other businesses like SpaceX," Fields said in an interview in July with CNBC's Brian Sullivan. "You can say to the president, 'Hey, you know Boeing are convicted felons, so give me a majority of your business.'"

Trump has also said he would place steep tariffs on goods from China, a market where Tesla faces growing competition.

Musk "knows that he may take a harder stance against China, and that may help them in the U.S., because that's one of their biggest and most profitable markets," Fields said.

'I have no choice'

Since gaining Musk's support, Trump has returned the praise.

"I think what he's done is great," Trump said at the Bitcoin Conference.

On Saturday in Atlanta, Trump continued with that theme, telling the audience that he was "for electric cars." He added, "I have to be, you know, because Elon endorsed me very strongly. So, I have no choice."

Musk, meanwhile, has been moving rightward politically for years, and not just in the U.S. He's developed relationships with Italian Prime Minister Giorgia Meloni, Argentinian President Javier Milei, former Brazilian President Jair Bolsonaro, Indian Prime Minister Narendra Modi, and in July he visited Capitol Hill as the guest of Israeli Prime Minister Benjamin Netanyahu, who delivered a speech to Congress about the war in Gaza.

Despite his vocal support of Trump, Musk appears to have stuck by his pledge not to donate directly to candidates this election cycle, going the PAC route instead.

Instead, Musk is using X to tout his preferred candidate to his 193 million followers.

On the day of Trump's speech in Nashville, Musk wrote "Save our kids!" along with a video of Trump in West Palm Beach, Florida, where he said he would sign an executive order to cut federal funding to schools "pushing critical race theory" and "transgender insanity."

And then there was Musk's retweet of a parody Kamala Harris campaign ad. The video features a voice that sounds like Harris saying she was picked because she is "the ultimate diversity hire." The video wasn't labeled as misleading, in what appears to be a violation of the platform's rules.

While Trump has his fair share of support in tech, going well beyond Musk, many in the industry are quickly rallying around Harris. As of this week, more than 750 people in and around venture capital signed the "VCs for Kamala" pledge, which was first announced on July 31.

In an op-ed in the Financial Times on Monday, legendary venture capitalist Mike Moritz took aim at Trump's supporters in Silicon Valley and said they're "making a big mistake."

"They are, I suspect, seduced by the notion that because of their means, they will be able to control Trump," Moritz wrote. "And, I imagine they are also committing another cardinal error: deluding themselves that he will not do what he says or promises." 

— CNBC's Brian Schwartz and Christina Wilkie contributed to this report.