If you didn't take the time to read the entire article you should. Even if you don't have statistical training, you don't have to agree with all parts or any of it, but it's at least an effort to put together a backed up thesis on what's happening. It's a good article and we'll written, but it has some major blindspots that need addressing.

First:

This points to three possible explanations: 1) we're wrong, and an unprecedented level of split-ticket voting will occur in the swing states, 2) a significant portion of Trump voters remain undecided in Senate races, or 3) these averages are reflecting a significant amount of noise.

There are more than 3 possible explanations, and anytime you see some one trying to box in what you are allowed or not allowed to consider as possible, your hackles should raise.

Second:

The article makes little mention or discussion of the candidates, their policies, their approach to campaigning. Which is fine, the article isn't necessarily trying to say why things are in such a way, but so much as saying, things maybe aren't in the way they appear. And that's a totally fair approach to take, but it assumes naivety or moreso, a kind of uniformity around the candidates and the campaigns themselves as if these people running are random effects. This is also baked into much of the statistical approaches they use in the article, which are all effectively coming out of the parameteric/ traditional stochastic world view of how to do these things. And that's fine, but it's an important assumption to key in on.

Third:

The point about flooding the zone has been thoroughly debunked. Sure there are more polls being released but even Times Sienna, Quinipiac, etc are showing largely the same things. Harris isn't winning in the polls. That just is what it is. So when they say "we should listen to the data", then they don't, well, that's at least a yellow card.

Something that needs to always be addressed is the possibility that Trump "is a different kind of candidate", which touches on points 1,2. I wish I had all the data worked up and on mobile it's just not worth my time to do so, but we need to talk about something specific about Trump, Trumpism, and polling. Look at Trump's performance on the ground in elections relative to polling in 16, and 20, and compare that to candidates he endorsed and campaigned for in 18 and 22. Trump has a unique property where they singularly defy their polling, and this property is not transferable. Trump massively outperformed his polling in 2016, and also in 2020. 2020 should not have been close, yet it was. Likewise, Trump seems to only be able to influence down ballot races with their presence. People are not showing up for Trump endorsements the way they show up for Trump. It's not about the party it's about Trump. He is able to drive out demographics that don't /aren't represented in extant sampling approaches to polling. His campaign strategy is to find blocks of voters that arent voting and to get them to show up (which was also the Bernie strategy). He'll always defy polling using this approach because his strategy is to literally grow the electorate.

The same kinds of issues need to be addressed on the Kamala side of the house too. These candidates don't sit in vacuum tubes insulated from the world. Biden was dead in the water literally a year before the primary got started: the insistence on running a clearly failing President significantly damaged the Democrats chances this cycle. Democrats didn't get to have Primary debates, which are literally billions in free marketing and an opportunity for a party to present their vision of how to proceed. It allows you to control and steer the narrative before getting going on the campaign proper, as well as to test messaging and get a better read on the electorate. Not primarying Biden will go down as one of the dumbest political malpractices of all time. Meanwhile, Biden has shown to be uniquely feckless in the face of its vassal state effectively defying orders, and committing to a policy of genocide and ethnic cleansing. The US is absolutely on the wrong side of history right now, and the Harris campaign owns that because they are the party in power. Not only that, but the Harris campaign has effectively doubled and tripled, down on thus strategy by aligning so closely with the neoconservative movement (not even popular with Republicans) that also advocates for a first strike, settler colonialism approach to global politics. The reason I bring this up, is because there are explanations for why polling looks the way that it is that don't require massive leaps in logic or a fundamental understanding of politics, but maybe do require you to adopt a more process based or non-parametric approach to analyzing election data.

It's a good analysis and maybe it's right. But what I can tell you right now, is that analyses that only rely on prior conditions have a hard enough time modeling the past, let alone the future. There is a reason why our climate models are missing the massive heating that seems to defy explanations in our current approach. There is a reason why insurance businesses globally have been caught completely off guard by the scale, severity, and frequency of natural catastrophes . It's because the past isn't a reliable indicator of the future, and if that's all you are relying upon, you'll only ever be able to make predictions in typical elections for the data set you are basing them on.