It may be a small fraction of the company, but activist investors in Apple and ExxonMobil have accomplished a lot, with a lot less.

Wall Street has countless stories of investors acquiring stakes in companies for which they seem like very bad fits—Bill Gates investing in Waste Management, America’s leading garbage company; Warren Buffett getting into American Airlines, Delta, United, and Southwest a few years after calling the airline business a “death trap.” Yet Republican...

Continue Reading Vivek Ramaswamy spent $3.3 million to buy 8% of BuzzFeed. How much damage could he do with that stake?