The Russell's outperformance "could easily dissipate if the bluntness of this trade policy is taken out," Luschini said. "You could get reversion pretty quickly."
While small caps appear to have benefited from the tariff talk, shares of companies that stand to see their costs rise have suffered.
The S&P 1500 machinery index has fallen more than 1 percent since last week while the S&P 1500 automobiles and components index has shed over 2 percent.
By contrast, the S&P 1500 steel index has climbed 5 percent in the past few days.
Some investors stayed away from recommending any significant shifts in portfolio strategies based on the tariffs, as uncertainty remained about their extent and timing with a formal announcement still to come.
“We are not spending a lot of time trying to handicap industries or sectors just because we think there are too many moving parts," said David Katz, chief investment officer at Matrix Asset Advisors in New York.
The risk from the tariffs themselves may be limited if there are no repercussions.
"Unless you have a 1950s portfolio of automakers, steelmakers and producers, you will probably not see much impact if you see the tariffs applied as they are being discussed," said Jason Ware, chief investment officer with Albion Financial Group in Salt Lake City, Utah. "However, the big question is where does it go?"
Despite Cohn's exit, some investors may be holding out hope the tariffs will fail to come to pass amid resistance from Republican lawmakers and other countries.
Trump looked set to authorize the tariffs this week as he stepped up pressure against China to develop a plan to reduce its trade imbalance with the United States by a billion dollars. However, stocks pared losses after the White House said late Wednesday that Canada and Mexico, and possibly other countries, may be exempted from the tariffs.