Tesla’s gain of more than 4 percent in Wednesday’s trading extended a recent surge in which its share price has more than doubled in three months. Along the way, Tesla’s market value surpassed that of General Motors and Ford Motor combined, reflecting a faith among some investors in the company’s ability to disrupt the automotive industry.

At the same time, the stock is also one of the biggest targets of short-sellers, ranking alongside much larger companies like Apple and Microsoft in interest from investors who hope to profit from what they see as an inevitable decline in the share price. According to S3 Partners, a financial technology and data firm, the number of Tesla shares shorted has hovered around 26 million or 27 million — about 20 percent of the shares available for trading — for some time.

“The amount is just telling you that the soap opera continues,” said Bob Sloan, the founder of S3 Partners. “The company’s stock has doubled, and the doubters are still the doubters.”

Tesla’s stock started surging in October when the company reported an unexpected profit for the third quarter after recording a $1.1 billion loss in the first half of 2019 as it struggled to produce and deliver its Model 3 sedan. Earlier, in September 2018, Mr. Musk had agreed to step down as chairman in a settlement with the Securities and Exchange Commission after it had accused him of misleading investors with a claim on Twitter about having “funding secured” to take the company private.

Even with that settlement, Tesla remains under regulatory scrutiny. Last week, the National Highway Traffic Safety Administration said that it was considering a request to investigate claims that some Tesla vehicles have accelerated on their own. The company dismissed the claims as “completely false” in a blog post. The author of the request, Brian Sparks, acknowledged in an interview with CNBC that he was shorting Tesla’s stock.