One of the biggest surprises on the midterm campaign trail is hearing President Obama echo President Reagan’s famous question by asking voters whether “you are better off than you were four years ago.” The question is the hammer in Obama’s toolbox for nailing down his Democratic majority in the Senate in this year’s midterm election. “By almost every economic measure, we are better off today than we were when I took office,” the president said in a Sept. 19 speech to the Women’s Leadership Forum, sponsored by the Democratic National Committee. Speaking to a Labor Day rally of union workers...