Right now, the 2016 stories are all about individual presidential candidates -- Hillary and Jeb and Rand and Ted and maybe Martin. But let's just put aside what they're eating for lunch, and try to predict which party is most likely to win the White House next year. Will the Republicans have a leg up after eight years of a Democrat in the Oval Office, or will the Democrats have an advantage because of an improving economy (assuming it keeps growing in the next 18 months)?