Billionaire Elon Musk has promised to give away $1 million each day until November's election to someone who signs his online petition, with the first prize awarded at a PAC event supporting Republican Donald Trump, raising questions about the legality of the payments.

Musk gave a $1 million cheque to an attendee of his America PAC event in Harrisburg, Pennsylvania, aimed at rallying supporters behind presidential candidate Trump. The winner was a man named John Dreher, according to event staff.

"By the way, John had no idea. So anyway, you're welcome," the Tesla founder said as he handed Dreher the cheque.

The money is the latest example of Musk using his extraordinary wealth to influence the tightly contested presidential race between Trump and his Democratic rival Vice-President Kamala Harris.

Musk started America PAC, a political action organisation he founded in support of Trump's presidential campaign. The group is helping mobilise and register voters in battleground states.

Pennsylvania Governor Josh Shapiro said Musk’s plan to give money to registered voters in Pennsylvania was “deeply concerning” and “it’s something that law enforcement could take a look at”.

Questions about the legality of these cash payments abounded, as election law experts pointed to various provisions in federal law that prohibited making cash payments to voters.

It is a federal crime to pay people with the intention of inducing or rewarding them to cast a vote or to get registered, an offence punishable by prison time.

The prohibition covers not only monetary expenditures, but also anything of monetary value like liquor or lottery chances, a Justice Department election-crimes manual says.

Elon Musk speaks at a recent Donald Trump rally. – AP

The Harrisburg event was the third in as many days in Pennsylvania, where Musk is painting November's election in stark terms and encouraging supporters to vote early and get others to do the same.

He said that if Harris wins, it will be "the last election".

He also said the two assassination attempts against Trump prove he is ruffling feathers and upending the status quo.

The petition Musk is asking people to sign reads: "The First and Second Amendments guarantee freedom of speech and the right to bear arms. By signing below, I am pledging my support for the First and Second Amendments."

Attendees of the event had to sign the petition, which allows America PAC to garner contact details for more potential voters that it can work to get to the polls for Trump.

Musk, ranked by Forbes as the world's richest person, so far has supplied at least $75 million to America PAC, according to federal disclosures, making the group a crucial part of Trump's bid to regain the White House.

The entrepreneur behind carmaker Tesla and rocket and satellite venture SpaceX has increasingly supported Republican causes and this year became an outspoken Trump supporter.

Trump in turn has said if elected he would appoint Musk to head a government efficiency commission.

A closer look at what’s going on

What is Musk doing?

Musk has promised that he would give away $1 million a day, until the November 5 election, for people signing his PAC’s petition supporting the First Amendment, which protects freedom of speech, and the Second Amendment, with its right “to keep and bear arms”.

He awarded a cheque during an event on Saturday in Harrisburg, Pennsylvania, to a man identified as John Dreher. Musk gave out another cheque on Sunday.

What’s the broader context here?

Musk’s America PAC has launched a tour of Pennsylvania, a critical election battleground. He’s aiming to register voters in support of Trump, whom Musk has endorsed.

The PAC is also pushing to persuade voters in other key states. It’s not the first offer of cash the organisation has made.

Musk has posted on X, the platform he purchased as Twitter before renaming it, that he would offer people $47 – and then $100 – for referring others to register and signing the petition.

Trump, who was campaigning in Pennsylvania, was asked about Musk’s giveaway, and said: “I haven’t followed that.”

Trump said he “speaks to Elon a lot – he’s a friend of mine” and called him great for the country.

What’s the issue with that?

Some election law experts are raising red flags about the giveaway.

Brendan Fischer, a campaign finance lawyer, said the latest iteration of Musk’s giveaway approaches a legal boundary.

That’s because the PAC is requiring registration as a prerequisite to become eligible for the $1 million cheque.

“There would be few doubts about the legality if every Pennsylvania-based petition signer were eligible, but conditioning the payments on registration arguably violates the law,” Fischer said.

Rick Hasen, a UCLA Law School political science professor, went further. He pointed to a law that prohibits paying people for registering to vote or for voting.

“If all he was doing was paying people to sign the petition, that might be a waste of money. But there’s nothing illegal about it,” Hasen said.

“The problem is that the only people eligible to participate in this giveaway are the people who are registered to vote. And that makes it illegal.”

Michael Kang, an election law professor at Northwestern University’s Pritzker School of Law, said the context of the giveaway so close to Election Day makes it harder to make the case that the effort is anything but a incentivising people to register to vote.

“It’s not quite the same as paying someone to vote, but you’re getting close enough that we worry about its legality,” Kang said.

A message seeking comment was left with the PAC, as was a request for comment from the Justice Department.

Can the PAC and Trump’s campaign coordinate?

Typically coordination between campaigns and so-called super PACs had been forbidden.

But a recent opinion by the Federal Election Commissioner, which regulates federal campaigns, permitted candidates and these groups to work together in certain cases, including getting out the vote efforts.