For the most part, the gay marriage debate now falls along partisan lines: Democrats support it, But within the crowded field of likely 2016 presidential contenders, there’s a lot of room for nuance. The would-be candidates have made much different arguments and have varying records on the issue. Meantime, the issue continues to change. On Jan. 6, Florida became the second-largest state to recognize gay marriage, bringing the total to 36. And on Friday, the Supreme Court will meet privately to decide whether to consider cases that could lead to a more definitive ruling in favor of same-sex marriage. Here’s...