PHILADELPHIA (AP) — When Bill Clinton takes the stage Tuesday night for his 10th address to a Democratic convention, the ex-president, husband and party standard-bearer will step into a singular role in American history: potential first gentleman.It isn't only Hillary Clinton who is breaking a glass ceiling this week. Should she win on Election Day, her husband will become both the first male to be a first spouse and the first former president to reoccupy the White House [...]