I think there are basically 3 groups of polls that herd.

1) Some (certainly not most or all) online or IVR polls with crappy raw data seem to look to live-caller polls for guidance. They tend to stay pretty close to the averages throughout the year. https://twitter.com/kmedved/status/1320777668565098496

2. Some partisan and quasi-partisan pollsters seem to play a lot of games with the 538 and RCP averages. They don't want to stray *too* far from the average, but they'll often show results that are like the 538 or RCP average shifted by 2 points toward their side.

3. Some high-prestige academic and media pollsters may be scared to publish a perceived outlier very late in the race, when they think it could hurt their reputation. For most of the year, these pollsters are the ones you trust NOT to herd. But sometimes their final polls are .

I guess that doesn't totally answer your question @kmedved but in general, the firms that are doing good enough work to diverge from the consensus *and have reason to think they're right about it* are the firms with good reputations that may not want to risk them.