The White House leaked word late Friday evening that the U.S. will impose a 35% tariff on imported Chinese tires used by millions of low-income Americans. We wonder if President Obama understands the political forces he's unleashing with this blatant protectionism. Mr. Obama is setting a precedent in the tire case because he is applying a previously unused part of the trade law known as Section 421. This allows U.S. industries or unions to seek protection from "surges" of Chinese imports, with a lower burden of proof than normal antidumping or countervailing duty cases. President Bush nixed the four Section...