Mr Musk on Monday said he planned to tour the key battleground state of Pennsylvania, giving talks to voters. The pledge came a day after he conducted a groundbreaking launch of his Starship space rocket.
The tech tycoon said: “If you’d like to attend one of my talks there’s no attendance fee. You just need to have signed our petition supporting free speech and the right to bear arms and have voted in this election.”
The funding from Mr Musk provides crucial additional cash to Mr Trump’s election campaign in the final weeks before the vote on Nov 5. The injection comes despite Mr Musk insisting in March that he would give no money to any candidate and denying reports he was planning a donation.
Since replacing Joe Biden on the Democratic ticket, Kamala Harris has raised more than $1bn in donations, securing the backing of billionaires in Silicon Valley and Hollywood.
However, Mr Musk is one of a handful of influential Bay Area investors and entrepreneurs who have given millions of dollars to Mr Trump. Some are criticising the Biden administration’s crackdown on cryptocurrency and tough stance on technology regulation.
US election filings also show that Miriam Adelson, the heir to a casino fortune, gave $95m to Mr Trump’s re-election campaign, further boosting his war chest.