Once upon a time, May 1 (May Day) was a day for working-class parades in factory towns. This year, it was a day for Joe Biden, setting off on his third presidential campaign in 32 years, to make news on the stump — not in a working-class venue but in the university town of Iowa City, now the state’s Democratic stronghold.

Biden’s claims for the presidency rest heavily on foreign policy expertise gained in eight years as vice president and 34 years on the Senate Foreign Relations Committee. Unusually for a Democratic candidate this cycle, he chose to speak about China. “China is going to eat our lunch?” he asked rhetorically. “Come on, man. They can’t even figure out how to deal with the fact that they have this great division between the China Sea and the mountains in the west. They can’t figure out how they’re going to deal with the corruption that exists within the system. They’re not bad folks, folks, but guess what? They’re not competition for us.”