Four years ago, Rick Perry led the pack during late summer, Herman Cain surged in the early fall, Newt Gingrich was surging by November/December, and then Mitt Romney took the lead and the momentum.
This is a pretty ridiculous comparison.
RCP averages vs RCP averages up to this point in 2011.
Note
A. that Trump has been leading for nearly two months now, longer than any of the 2011 flavor of the month candidates. Perry had a huge media wave relating to his Labor Day weekend late entrance into the race that propelled him into #1.
B. More importantly, note how well Mitt Romney was doing even at the height of Perry's surge. By the end of September Mitt will be back over 20% and never drop below that line again, and is closer to 25% for most of the rest of the race, during periods he'll be basically tied with Cain and Gingrich. Trump, on the other hand...is by himself. Jeb Bush is polling about as well as Ron Paul was at this time four years ago, and Carson is just starting to break from the pack.
There's a giant Romney-shaped hole in the 2012-2016 comparison. That and Trump has
already proven more durable than any of the flavor of the month candidates: he'll be celebrating two months leading the polling averages next Monday. Gingrich, the longest-lasting of the 2012 guys, made it a month and a half.