Two things about 2008 Iowa/Obama that I want to flag.
1. The social landscape 2008 vs. 2024. Social media was more of a curiosity reserved for tech-savvy and college-aged people, which meant that people were far less ideologically and socially segmented in 2008 than we are today. For those who believe in monoculture, there was a stronger monoculture in 2008 than today, which means a place like Iowa could give you a sense for what middle america is thinking.
Today? We have Elon and Zuckerberg curating what everyone sees, reinforcing bubbles and echo chambers, replacing Tom Brokaw and Dan Rather with Dan Bongino and Democracy Now!. The media diet of the average Iowan may not resemble the media diet of the average Pennsylvanian, and their values and voting are more likely to reflect those differences. I think Selzer is a fantastic pollster who knows Iowa better than any pollster knows their respondents, but I would read far less about the national landscape into her polls today than I would in 2008.
2. The political landscape 2008 v. 2024. Obama was a generational talent who tapped into a powerful desire to reject the Bush era. 2024 on the other hand offers two paths that most voters feel like we've been down before: Trumpist chaos-through-fascism vs. Biden-esque stability-through-neoliberalism. With Harris, there is no longer the concerns about age and stamina, and she has made a deliberate point not to emphasize her gender or race. With Trump, there is no longer the pesky global pandemic to dampen his ability to run on his record.
With neither candidate in a position to offer anything that feels new to the voters, this might be the first race in recent memory to be a dueling referendum on diametrically opposite values systems, both of which the American people have test driven.