The 2012 Republican presidential contest is the most volatile since at least 1964, Gallup has determined.
The prominent polling firm said Monday that with four distinct national frontrunners since May -- and the lead changing seven times in that period -- the only comparable Republican contest is the 1964 primary which then-Sen. Barry Goldwater eventually won.
In that race, though, the volatility appeared only after primary elections began. Goldwater and Nelson Rockefeller were the lone frontrunners at the start of the race -- later on, three other candidates would emerge at the front of the field, including Richard Nixon, before Goldwater's win.
In this early pre-primary stage of the 2012 contest, Gallup reported that the "Republican nomination process has been the most volatile for the GOP since the advent of polling."
The race could still have a few more unexpected turns in store. According to national figures, the lead has been traded or shared by Mitt Romney, Rick Perry, Herman Cain and Newt Gingrich since May. But in Iowa, both Ron Paul and Rick Santorum have surged and could be in contention to pull off a strong showing in Tuesday's caucuses.
The Gallup report noted that "the start of actual voting" could result in "additional national preference swings before the nomination is settled."
Gallup compared the 2012 race to the 2004 contest for the Democratic presidential nomination, in which the lead changed nine times through 2003. Voters eventually settled on Sen. John Kerry.