The federal deficit is expected to shrink to $642 billion this year, half of what it was four years ago, the Congressional Budget Office estimated on Tuesday. Sen. Bernie Sanders, a member of the Senate Budget Committee, welcomed the news. He cautioned, however, that the budget should not be balanced on the backs of seniors and children. And he called for rebuilding the country’s crumbling infrastructure to create millions of jobs, stimulate the economy and help working families. “We must not place ourselves in a situation in which the operation was a success but the patient died, and the patient that I am talking about, of course, is the disappearing middle class, the backbone of this great country.”