“The market is punishing them harshly for that,” Mr. Whiston said.
It may be harder for Tesla to pass G.M. a second time. Auto sales in the United States are slowing over all, and Tesla is not yet a significant player in China, the world’s largest auto market. In the second quarter, Tesla produced more cars than it delivered to customers, causing some analysts to question whether demand for current models — the Model S sedan and the Model X, a sport-utility vehicle — is reaching a plateau.
While Tesla is by far the most successful producer of battery-powered electric cars, analysts believe traditional automakers will catch up fairly soon. This week, Volvo, the Swedish company, stole some of Tesla’s thunder by saying that all its models would be hybrid or fully electric vehicles by 2019.
With established manufacturers expanding their electric options, “Tesla will face intense competition by the next decade,” Brian Johnson, a financial analyst at Barclays, wrote in a note to clients.
But by far the biggest concerns are related to the Model 3.
Until now, the company has produced the Model S and Model X, which can sell for $70,000 and up, in relatively small numbers. In 2016, Tesla made about 85,000 vehicles. But the Model 3 will be priced at roughly $35,000 and is aimed at a wider range of buyers. With the Model 3 in the lineup, Tesla expects to sell about 500,000 cars a year by 2018.
Last year, Mr. Musk predicted that Tesla would sell about 100,000 Model 3s this year. But late on Sunday, outlining a production plan on Twitter, he said the company expected to make 30 this month, 100 in August, and 1,500 in September. He expected production to climb to about 20,000 cars in December. That would leave it well short of 100,000.
Concern over Model 3 production was compounded when the company said its giant battery plant in Nevada had struggled to produce enough battery packs.
“Up to now, Tesla has had little experience with volume production,” Axel Schmidt, managing director of the automotive practice at Accenture, a large consulting firm, said in an email. Ramping up Model 3 production “remains a huge challenge,” he said.
The slump in Tesla’s share price halts a remarkable surge for the company, in which its stock rose from a little over $180 in November to more than twice that recently.
A year ago, Tesla stock was shaken by news that an owner of a Model S was killed when his car, operating in the company’s self-driving mode known as Autopilot, failed to see a tractor-trailer crossing a highway in Florida.
The crash raised questions about the reliability of the technology and about whether Tesla had overstated its capability in its marketing, and even in using the name Autopilot. Federal agencies opened investigations, including one to determine if there was a safety defect in Autopilot.
The stock price languished even after Mr. Musk laid out an updated “master plan” for the company, with a pledge to expand beyond electric cars into battery-powered pickups, semi-trailer trucks and buses, and to equip them with advanced self-driving systems.
But this year, investors began focusing on the introduction of the Model 3 and Mr. Musk’s confident prediction that Tesla would be able to increase sales fivefold next year.
Tesla raised $1 billion in stock and debt offerings to bolster its coffers in advance of the Model 3 introduction. The National Highway Traffic Safety Administration concluded its investigation of the fatal crash and found no defects in Autopilot.
April brought more good news: a strong jump in vehicle production in the first quarter, and a new surge in the stock price that pushed Tesla’s market value to $48 billion, surpassing the market capitalization of Ford Motor. The run continued, and on April 10, the stock surged to $312.39.
That made Tesla more valuable than General Motors, a company that last year produced more than nine million vehicles and earned $9.4 billion. Tesla, by comparison, produced about 85,000 cars last year and reported losses in most of the last several quarters. In the first quarter of this year, it lost $397 million, compared with a loss of $282 million in the same period a year earlier. The company’s revenue more than doubled, however, to $2.7 billion.