Elon Musk spent at least $445 million to help Republicans retain control of the US Congress in the midterm elections, but the massive investment failed as Democrats secured a series of victories, including in Texas, where the billionaire has based himself and several of his companies.

The election results have also exposed Musk to potential congressional investigations and renewed scrutiny of his companies' dealings with the federal government and state authorities.

While President Donald Trump suffered major political setbacks on Tuesday, few Republican supporters had as much at stake as Musk, whose companies depend on billions of dollars in government contracts, grants and other benefits.

Democrats, who have long been critical of Musk, are now preparing to examine his businesses and his work at the Department of Government Efficiency (DOGE), with possible subpoenas and investigations.

Musk joked about the outcome on X, the social media platform he owns, writing: “Guess my election-interfering space lasers didn't work this time,” alongside a shrug emoji.

Democrats make historic gains in Texas

Musk's political spending also failed to protect Republican candidates in Texas. He spent at least $5 million to help Republican Governor Greg Abbott secure re-election, but Abbott lost to Democrat Gina Hinojosa.

Democrats also won control of the Texas House and the US Senate, defeating Republican Attorney General Ken Paxton, who had effectively benefited from $158 million in Musk's spending. Paxton lost his Senate race to Democrat James Talarico.

The victories marked the first statewide electoral wins for Democrats in Texas in more than 30 years. Democratic candidates repeatedly criticised Musk's political influence, the tax breaks and grants received by his companies, and his relationships with Republican politicians.

“This era of open corruption is going to come to an end,” said Rep Gene Wu, chairman of the newly empowered Democratic Caucus in the Texas legislature.

Musk did not respond to requests for comment.

According to an AP Voter Poll of more than 5,000 Texas voters, slightly over half had an unfavourable opinion of Musk. Although he remains popular among supporters of the MAGA movement, his approval is considerably lower among other Republican voters, independents and Democrats.

Talarico and Hinojosa focused their campaigns on the contrast between billionaires and ordinary Texans, making Musk's role as a major Republican donor a central issue.

“Paxton is funded by one dude. Elon Musk wants our land. He wants our water. He wants our tax dollars. He wants his very own personal United States senator,” Talarico told supporters at his final campaign rally.

Hinojosa also criticised a $1.7 billion property tax break Musk received in Texas, saying ordinary residents had to pay their taxes in full.

Musk's financial support helped fund extensive negative advertising against Talarico, but Democrats maintained that rising costs of fuel, groceries, rent and mortgages were more important concerns for voters.

Outgoing Republican Rep Chip Roy said there was a limit to how much political donations could help a campaign.

“People are so turned off by all of the ads, and all you’re doing is running the same ad every single time,” he said.

Election results weigh on Musk's wealth

Shares of Musk's publicly traded companies, Tesla and SpaceX, fell sharply on Wednesday, even as the technology-heavy Nasdaq composite index rose.

Tesla's share-price decline erased around $40 billion from its market value, which stood at $1.54 trillion. SpaceX also lost about $40 billion in market value, bringing it to $1.83 trillion.

According to Forbes, Musk's personal wealth dropped by around $45 billion to $865.6 billion, although the loss could be reversed.

Investors are concerned about the potential impact of the election results on his businesses, particularly the possibility of congressional investigations.

Joe Mazzola, head trading and derivatives strategist at Charles Schwab, said concerns about possible investigations had contributed to the early decline in shares of Musk's major companies.

Michael Morris, a professor of leadership at Columbia Business School, said Musk's business success might have led him to believe he could exert similar influence over politics.

He said Musk had more money than he would ever need and his companies were performing well, adding that political involvement might be a kind of game for him.

Democrats prepare to scrutinise Musk's businesses

Democrats have not forgotten Musk's role in Washington last year, when he headed DOGE and oversaw sweeping cuts to federal agencies and public-sector jobs.

They have also criticised a recent controversy involving Starlink, SpaceX's satellite internet service, which was throttled in Ukraine amid its war with Russia.

Virginia Democratic Rep James Walkinshaw called for Musk to answer questions under oath, recalling his public appearance with a chainsaw while announcing cuts to government services.

Musk's businesses could also face increased scrutiny in Texas under the incoming Democratic administration.

In August, his companies received a $30 million grant through a state programme to build a semiconductor plant expected to create 3,000 jobs. The grant was among several financial benefits his businesses have received through state programmes.

Musk has also successfully lobbied the Texas legislature to pass laws favourable to his companies.

During the election campaign, he repeatedly attacked Talarico on X over the Democrat's positions on transgender rights and other progressive issues. Such cultural issues were also central to Paxton's attacks on Talarico, but failed to secure him victory.

“You know you couldn’t pull the wool over their eyes anymore with these culture wars, and they are frustrated with the costs,” said Rep Christina Morales, a Houston Democrat.

“We’re not saying you don’t belong here,” she said, adding, “but Texans can’t be bought.”