Investors should be hesitant to "connect the dots all the way to the presidency," David Rosenberg, Gluskin Sheff chief economist, said in an interview Tuesday on CNBC's "Squawk on the Street."
While the market is rising, the stocks and sectors that were penned "buys" if Trump won the election have actually underperformed over the past several months, Rosenberg said.
Instead, factors sparking the trends should be seen on a global scale, and Trump's role should be put "on the back burner next to everything else going on around the world," he said.
Global factors include the stabilization of Chinese economic growth; the containment of Brexit, which didn't lead to a French 'Frexit' withdrawal as predicted, and German Chancellor Angela Merkel's higher-than-expected ratings, according to Rosenberg.
"You can't just look at one thing and say, 'Well, this is what explains what's happening with the stock market,' when it really is, to some extent, a global stock market," he said.
Others, however, attribute the market optimism to Trump's proposed tax reforms.
"The stock market is a discounting mechanism that looks to the future," said Charles Bobrinskoy, Ariel Investments vice chairman. "It brings back future earnings to the present, and right now, the stock market is still expecting cuts in corporate taxes, a friendlier work environment for U.S. companies."
Bobrinskoy proposed a thought experiment: Suppose Trump stopped plans for tax reform tomorrow, and the administration said there won't be a change in the corporate tax rate.
"What would happen to the stock market?" Bobrinskoy asked. "It'd get killed. So the market is absolutely up because of expectations that Republicans in general — don't put it on Trump — Republicans are going to be successful in creating a more business-friendly environment."
Confidence is key in maintaining the market boom, Bobrinskoy said, estimating Trump's reforms will usher in a 27 to 28 percent marginal tax rate. And if the reforms could promise something as low as 25 percent, "the stock market would be up significantly on that news," he said.
"So long as people still have the same confidence that it's coming, it doesn't make that much difference," Bobrinskoy said in an interview on "Squawk on the Street." "That's why the delay in the tax reform is not that big a deal. What is a big deal is if people start losing confidence in its inevitability."