Andrew Left is breaking a promise, and very few people would blame him.

Left, the legendary short seller behind Citron Research, is back at shorting Tesla Inc. TSLA, -4.14% stock, which on Tuesday rose nearly 14% to close at a record $887.06, its sixth straight session of gains.

“This is obviously a computer-generated rally, it’s not a reflection on the company, or on valuation. It’s just a trade,” Left told MarketWatch. “Yes, I'm shorting it…whoever bought it at these prices has to flush it out, and when it flushes, it’s going to flush hard.”

Earlier on Twitter, Left compared Tesla’s rally to a casino and indicated he was back at shorting it:

The stock hit an intraday record of $968.99 before paring gains into the close. It has already more than doubled (up 112%) in 2020.

Andrew went long on Tesla in October 2018, praising the Model 3 and saying that other car makers had been “taking the Ambien,” a medication to induce sleep, while Tesla leapfrogged them to become the dominant EV maker. Back then, Tesla traded under $300, a level it would stay, give it or take it $50 on either side, for another year.

See also:Tesla’s stock soars above $900, boosts value of Elon Musk’s stake by $6 billion

Tesla is the No. 1 most shorted U.S. stock, with 24 million of its shares, or about 18% of its float, in the hands of short sellers, or those who bet a stock will fall in price.

According to financial technology and analytics firm S3, the number of Tesla shares shorted have decreased by 1.37 million shares, or 5.30%, over the past month as the stock had risen nearly 50%. Over the past week, shorts have declined by 651,000 shares, or 2.6%.

To short a stock, investors must first borrow an already purchased stock so they can sell it, with the expectation that the stock can be repurchased at a lower price for a profit, before the shares are returned. If prices rise, however, the short seller could be out of luck. And while the risk to buyers of a stock, known as “longs,” is limited to drop to $0, a short seller’s risk is unlimited.

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Other well-known Tesla skeptics include Kynikos Associates’ Jim Chanos, who in November reaffirmed his bearish stance on the company, and David Einhorn of Greenlight Capital. MarketWatch requests for comment from both firms weren’t immediately returned.

While funds like Greenlight are required to disclose their “longs” on a quarterly basis, in 13F filings with the Securities and Exchange Commission, they are not required to disclose short positions. The New York Stock Exchange and Nasdaq exchange disclose only the total number of shares shorted, every two weeks.

Tesla stock has hit high-water marks that stretch back to December, most recently fueled by a blockbuster quarterly earnings beat and the company’s promise it would sell more than half a million cars in 2020.

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Analysts at Wedbush, led by Dan Ives, called the Tesla rally “a parabolic run for the Wall Street history books” in a note Tuesday. The “bull party” will likely continue in part thanks to “very strong” production and demand in China, they said.

Moreover, the sales goal of 500,000 vehicles “is well within reach” and Tesla could hit “the elusive 1 million overall delivery vehicle mark potentially two years ahead of our original 2024 projections given this current trajectory aiming now in late 2022/2023,” the analysts said.

Earlier Tuesday, Tesla’s enterprise value surpassed Ford Motor Co.’s F, +3.70% , becoming the No. 1 U.S. car maker by that metric for the first time. Its market value of around $165 billon already had surpassed both General Motors Co.’s GM, +0.40% and Ford’s, with a market cap of $50 billion and $36 billion.

Ford later Tuesday reported fourth-quarter earnings that missed Wall Street expectations and shares fell more than 10% in the extended session.