Tuesday brought an intraday reversal to the stock market. The Nasdaq Composite (NASDAQINDEX:^COMP) jumped out to a solid gain by the middle of the day, but by the end of the session, the index was down almost 1%. The Nasdaq 100 saw similar declines, motivated in large part by calls from major players on Wall Street that the stock market's huge rebound from the March lows might have gotten ahead of itself.

One part of the market that has seen plenty of froth has been the electric vehicle (EV) industry. Although leader Tesla (NASDAQ:TSLA) managed to gain more ground today, newer players like Nikola (NASDAQ:NKLA) and Workhorse Group (NASDAQ:WKHS) suffered substantial declines. That has investors wondering if the momentum-based trading strategies that have worked so well lately could now be coming to an end.

Nikola hits the brakes

Nikola saw its stock drop 18% on Tuesday, building on losses from Monday's session as well. Today's drop came as stock analysts started to pile on against the electric truck specialist.

RBC started covering Nikola stock today, and it issued a sector-perform rating, which is essentially neutral. The stock analyst company also set a price target of $46 per share -- a level below where Nikola stock closed on Monday. The primary objection against Nikola is that the upstart company hasn't yet come far enough in its evolution. Until it can start posting real revenue, it'll be tough for stock analysts to assess the likelihood of success for the EV company.

Nikola Badger pickup truck in gray, in a desert landscape and overcast sky.

Image source: Nikola.

Nikola does have a promising story to tell, though. Setting up plans for a vertically integrated business that includes not only trucks but also the infrastructure to refuel them using hydrogen fuel-cell stations is a smart move, and it could help Nikola avoid the missteps some other companies have made in trying to displace diesel-powered commercial trucks.

The big question is whether Nikola can take the huge interest it's gotten for its commercial vehicles and its Badger pickup, and turn it into sales as effectively as Tesla has. If not, then today's stock-price decline will be justified.

Workhorse slows down

Nikola saw the biggest declines, but it wasn't the only EV company to lose ground. Workhorse Group's stock fell 4%, continuing its decline since late last week.

It's easy to understand what sent Workhorse up so sharply over the past month. The company's C-Series commercial vans passed federal motor vehicle safety standards in late June, allowing Workhorse to start selling them in the U.S. market. That was a huge milestone for Workhorse and proved the viability of its vehicle concept.

Yet there's only so much room in the EV market, and with Tesla having a commanding lead, investors seem to be reassessing the chances for multiple players. Tortoise Acquisition (NYSE:SHLL), which is slated to merge with privately held EV player Hyliion, saw its shares drop 9% today as well.

High-flying stocks can rise for a long time on speculation. Eventually, though, they have to prove themselves. Until these electric vehicle manufacturers can show how successful they'll be through top-line and bottom-line numbers, investors have to expect occasional turbulence like the stocks suffered today.