Trump, the bombastic businessman, has emerged as the likely Republican presidential nominee, partly fueled by strong rhetoric against trade deals and China. Britain, meanwhile, will vote on a possible exit from the European Union, a decision that some argue could shake its economic growth and broader expansion in Europe.
David Zervos, chief market strategist at Jefferies, believes both Trump's rise and a possible "Brexit" could drag on investors' returns.
"The two big events for me are Brexit and the election. They really make it a tough trading environment," he told CNBC from the sidelines of the Milken Institute Global Conference in California.