Elon Musk is making some big promises while campaigning for former President Donald Trump. But his business record calls into question whether he can deliver.

Musk, the richest man in the world with a net worth of $242 billion, according to Forbes, has pledged to give away $1 million a day to voters for signing his political action committee's petition backing the Constitution, a pledge experts say raises legal questions.

Mr. Musk, a megadonor, had flummoxed some Trump advisers by previously declining to write a “super max” check directly to the former president’s campaign.