If Hillary is the Democrats' nominee....

[President Johnson]

I'd give a slight edge to Republicans.

Parties always lose support after enough time in the White House. Hillary will not be able to distance herself from an increasingly unpopular President Obama. Her decades in public life mean she has a fairly high floor, but that she is also a poor agent for change. Demographic trends favor Democrats in the long term, but not quickly enough to have an impact here.

She's likely to be the Democrat's McCain, a respected figure who polled well initially, but got the nomination in the wrong cycle.

The big unknown is the significance of the first female President. We just don't know if there are enough Republicans or conservative-leaning independents who believe that milestone is worth a third term of Democrats in the White House.

Despite Obama's current unpopularity, I'm sure it's going to be more like 1988. Hillary will probably win, but she'll be defeated in 2020 by a moderate republican.

[President Johnson]

With the 1988 comparison I wasn't thinking about the specific percentage points; I thought more about the fact, that Reagan, in this case, was succeded by a man from his own party. Usually the partisanship of presidents alternates with each new officeholder, unless a vice president assumes the presidency without an election.

In 1988, Republicans won the third straight presidential election, but Bush then lost his bid for reelection four years later. This might happen again: Hillary wins in 2016, but loses in 2020 to a Republican, because Americans are tired of twelve years with Democrats in the White House.