Hillary Clinton shouldn’t be so quick to write off her recent string of Rust Belt losses to Bernie Sanders. While they won’t spell an upset in the Democratic primary, they do portend similar losses in the general election to Donald Trump, who has a wide lead over her on the issue of handling jobs and the economy. Exit polls in West Virginia and Indiana show Democratic voters see jobs and the economy as the top issues facing the country, and they think global trade is hurting American workers. Growing anxiety over the economy, which is softening in President Obama’s final...