October 30, 2013 year of the Four Emperors
I just looked at the year’s polls for the 2016 nomination. The various polls have denominated four different front-runners (see polls here). At the start of the year, nearly every poll denominated Marco Rubio as the front-runner.
Since May, Rubio has held first place in not one poll. The lead has been traded back and forth between Chris Christie, Ted Cruz and Rand Paul. (I note that in every poll, the front-runner’s lead has been too small to be statistically significant).