Reuters / Kyle Grillot

Tesla short-sellers are having a tough start to 2020.

Traders betting against the automaker have roughly $2 billion in mark-to-market losses so far this year, according to data from the financial-analytics firm S3 Partners.

That's a steep loss only seven trading days into 2020. The losses are due to Tesla's most recent rally — shares surged 18% through Wednesday's close on solid vehicle-delivery numbers and optimism about the company's new Gigafactory in Shanghai.

In 2019, traders betting against Tesla had $2.9 billion in mark-to-market losses for the entire year, according to S3. At the start of 2019, Tesla was a profitable short, as the stock lost roughly 46% between January and the yearly low in June.

But since then, Tesla has rebounded. The stock price has nearly doubled since October, when Tesla posted a surprise return to profit in its third-quarter earnings. The rally has also pushed its market value to roughly $89 billion, making it the highest-valued US automaker ever and worth more than the market values on Wednesday of its rivals Ford and GM combined.

Read more: A Wall Street firm unveils its 13 top stock picks for 2020 — including 4 healthcare names that could spike 150%

At least two Wall Street analysts think that the recent highs could be a peak for Tesla. CFRA on Wednesday downgraded Tesla to "sell" from "hold," and Baird on Thursday downgraded the stock to "neutral" from "outperform."

Even one analyst who did not change his rating issued a warning about Tesla's recent climb.

"We have become incrementally cautious on the stock, given its huge recent surge in price," Toni Sacconaghi of Bernstein wrote on Thursday.

In addition, he said, there's the potential for "weaker margins in Q4 and seasonal softness in Q1 following subsidy eliminations in the US and the Netherlands." Sacconaghi has rated Tesla "market-perform."

Shares of Tesla traded down as much as 3.8% on Thursday.

Markets Insider

NOW WATCH: A big-money investor in juggernauts like Facebook and Netflix breaks down the '3rd wave' firms that are leading the next round of tech disruption