The latest poll out of Iowa. This one was conducted by Iowa State University:
Others: 2% or less
The striking thing about this one to me is that Buttigieg here is shown to have more than double national frontrunner Joe Biden's level of support in the first state to vote, including more support than Biden among non-white voters (with whom he famously struggles nationally) in Iowa. This latest data makes it very clear that the ascendancy of Pete Buttigieg is coming one-sidedly at Biden's expense. No wonder Biden is on this bus tour through Iowa at this moment. He seems to be struggling not so much to win as simply for relevance there. (You'll also notice that Mayor Pete rarely criticizes Biden. He's accomplishing this feat without hardly critiquing Biden at all. That's further evidence that he knows exactly what lane of the party his campaign falls into.)
Still though, the key for Biden really is winning in South Carolina and Nevada. Those are really his first two must-win states, given who his base of support is overall. He doesn't actually need to win in either Iowa or New Hampshire. I mean, if the vote were held today, it's seems apparent to me that Buttigieg would win in Iowa, Bernie Sanders in New Hampshire, Biden in South Carolina and Nevada, and things would go from there. That's where we presently stand according to the latest polling data out of each of those states. None of it's too surprising either. Buttigieg is a well-spoken centrist candidate from the Midwest. Sanders is from a rural state that immediately borders rural New Hampshire. And Biden is President Obama's former VP. So there you go.
(Also notable: this data suggests that Pete Buttigieg's support is now about equal across all age groups in Iowa, skewing only slightly older.)
That said, if Buttigieg were to lead Biden among voters of color in early states like Iowa, I think that could change up the politics of his lane of the party, which is voting based on perceived candidate electability more than absolute policy agreement. Those voters could start to see Pete as more electable than Joe Biden if the numbers you see above are what actually happen in the Iowa Caucus, and that could change everything. The familiarity of Joe Biden forms a strong bias for more conservative Democrats to overcome in order to become willing to switch, but somethig like what you see above, if realized, could just do the trick.
As to why the ascendancy of centrists nowadays? Well, for those who haven't seen this before, or haven't paid much attention, that's how it works: usually the first people to start paying attention to elections are activists, so that's mostly progressives when it comes to the Democrats. But as you get closer to actual voting time, more moderate people start to pay attention. So initial polling indicating the ascendancy of progressive candidates often happens, but tends to be misleading for this reason. It's one of the reasons I avoid getting too optimistic about the chances of a progressive victory.