In the latest Gallup GOP national poll, Mitt Romney (21 percent) and Newt Gingrich (22 percent) are in a statistical tie among registered Republican and Republican-leaning voters. Herman Cain has dropped to third (16 percent), with Texas Gov. Rick Perry (8 percent) now behind even Rep. Ron Paul (R-Tex.) (9 percent).

What is interesting is the Gingrich surge at the onset of his first round of rigorous scrutiny has him much lower than the peak for Perry (29 percent). A GOP operative says he’s not surprised. “[Gingrich is] more of a known commodity, and not always in a good sense. Therefore he’s less likely to see a full-scale swoon.” Republican consultant Tony Fratto says the terrain is also different now than when Perry entered with a splash. He tells me, “Perry and Cain haven’t lost all of their elevated support, just part. So there’s less for Gingrich to capture. And Romney’s support stays fairly consistent.”

In any event, we know the pattern all too well. A potential unifying conservative enters the race. His shortcomings aren’t well-known. Then they become well-known. His poll numbers crash. The cycle repeats itself with another rival to Romney.

So, really, the question of the moment remains: How far and fast will Gingrich fall as voters learn more about him? It’ probably not a good sign for him that he starts at a comparatively lower altitude than those who tumbled previously.