Bernie Sanders on Monday evening confronted head-on questions regarding Joe Biden’s fitness for the presidency — declining to directly attack his rival’s stamina, but suggesting that brief speeches last week by Biden on the campaign trail were insufficient to address the nation’s problems. The remarks from the Vermont senator targeting the former vice president came at a Fox News town hall for Sanders, where a participant charged that Biden’s answers “don't make sense” and asked Sanders whether it was “acceptable” for a White House hopeful to answer questions “like Joe Biden does.” Sanders said that when his campaign conducts events...