Trump, like Perry and Gingrich, topped out at a bit above a 10-percentage-point lead. But then that lead held.
Here's what that graph looks like now:
We've increased the scale, because we wanted to add another 2012 polling surge into the mix: The final surge that gave Mitt Romney the nomination.
You don't have to think very hard about this to see why we should not immediately start assuming that Trump's upcoming trajectory will mirror Romney's. That Romney surge happened as primaries were already taking place, after all, and the increase in support was mostly a consolidation as his eventual victory became obvious. His (final) surge started Feb. 29, 2012.
It's also easy to note that not every about-to-win-the-nomination surge looks alike. They all look different. Here are the polling average leads for each of the last three nominees. The surges for John McCain and Barack Obama started on Jan. 11, 2008, and Feb. 13, 2008, respectively.
And we will also note that at this point in history, polls are not very predictive! I mean, we made a Twitter account to reinforce that fact.
The lesson, then, is this: What's happening with Trump in the polls is unusual by recent standards. No one who wasn't leading earlier in the year has gained and sustained a lead for this long — at least since 2008, which isn't a lot of data to work with.
But why would we be surprised? Nothing about Trump's campaign looks much like other recent runs for the White House.