Former Maryland Gov. Martin O’Malley is proposing to expand Social Security, part of a bid to cast himself as a progressive but practical candidate for the Democratic presidential nomination. According to a white paper shared by the campaign, O’Malley will set himself apart from frontrunner Hillary Clinton by calling for increasing the number of Americans with access to adequate retirement funds by 50 percent over two terms in office. “Social Security is one of our country’s greatest collective achievements,” the white paper says.