Nvidia's and Palantir's stocks have more than doubled this year, but Wall Street is bullish on one and bearish on the other.

Nvidia 's (NASDAQ: NVDA) share price has skyrocketed more than 800% while Kamala Harris has served as vice president of the United States. That's a bigger gain than the stock delivered when Donald Trump was in the White House. It's also larger than the returns generated during any of the four-year terms of Barack Obama and George W. Bush.

After days of exhibiting a possible turnaround an expert is warning that more losses could be in store for Nvidia stock.

Assuming Nvidia does reach $600 billion in sales in 2030, the stock will have to maintain its current price-to-sales ratio (P/S) of 32 to generate 561% returns from this level. That would translate into a market cap of $19.2 trillion, compared to the current level of just under $3 trillion.