Donald Trump has spent months courting one of his biggest donors, part of a sustained push to shore up Republican coffers before a midterm season the party expects to be brutal.

The effort paid off in May, when Elon Musk boarded Air Force One to join the President for his summit with Xi Jinping in Beijing.

There, Musk told Trump exactly what he wanted to hear: he intends to spend at least $100 million on Republicans in November to help the party hold Congress, according to the Wall Street Journal.

The reunion caps a campaign by Trump's closest aides to repair a relationship that ruptured in public just over a year ago.

The friendship collapsed in June of last year, after the world's richest man claimed Trump was blocking the release of the Jeffrey Epstein files because he was named in them. Trump threatened to cancel Musk's government contracts and branded him a 'big time drug addict.'

Susie Wiles and JD Vance began working to repair the rift within a day of the blow-up, the Journal reports. 

They believed that with insults that severe already public, there was little left to lose in trying to lower the temperature.

But the ceasefire has limits. Even with Musk's nine-figure pledge on the table, Trump has told advisers privately that the two will never be as close as they once were.

Still, the reunion serves both men. Democrats have said that if they win control of Congress they will open investigations into Trump and his family's business dealings, as well as into Musk, whose companies including SpaceX and Tesla depend heavily on government contracts.

Recent polling suggests Republicans could lose their Senate majority, with incumbent GOP senators in Maine, North Carolina and Ohio trailing their Democratic opponents.

Among the biggest drags on the party is the economy, particularly inflation, which many analysts attribute to the fallout from Trump's war with Iran. The national average price of gas now stands above $4 a gallon.

Vance played a key role in mending the Trump-Musk alliance by keeping lines of communication open, according to the Wall Street Journal.

Over the following months, as the vice president continued talking with the billionaire and his allies, Musk shelved plans to launch a third party rather than jeopardize the relationship.

Vance, for his part, believed Musk was too valuable a figure for Republicans to lose, the report said.

The president's eldest son, Donald Trump Jr., also stayed close to Musk, and his firm 1789 Capital invested in xAI, SpaceX and Neuralink around the time of the split. 

Another link ran through Katie Miller, wife of deputy chief of staff Stephen Miller, who worked with Musk during his White House stint.