2016, and I'm pretty confident about it.
3rd term same party rule isnt the norm; but the division among GOP, between Tea party and GOP, is similar to what the Dems went through in 2000; which cost Gore the election due to the Green Party Nadar.
Dems are united behind Hilary.
Even though the GOP looks very divided now, I think Republicans (myself included) want to win in 2016 so badly that even someone like Bush would win the votes of people who stayed home for Romney last time. I recently saw a poll that showed that a majority of GOP voters are more concerned with winning this time than having an ideologically pure candidate.