Presumptive Democratic presidential candidate Joe Biden announced his pick for vice president today, but the far larger question is what would he do about China? He has said he will eliminate Trump tariffs and work with allies to pressure Beijing but there should be skepticism about the effectiveness of that approach. Mr. Trump this week again urged the WTO to remove China’s self-designation as a developing country. Again, there is little likelihood of that changing. He could threaten to similarly declare the U.S. a developing country, which would highlight the audacity of the Chinese position.  President Trump is a believer in leverage, and he has used it in every manner possible. Some say his battle with China over technology...