Why is DuPage County, IL so far left and liberal?

[Unelectable Bystander]

Trump was a horrible fit for it.

Bear in mind that it's not really a Gwinnett situation where there was a ton of demographic change because it's barely grown in the past two decades. Downballot Republicans still do far better than Trump, and a non-Trump R should be able to do substantially better. Interestingly, it swung 15 points left between 2012 and 2016 but only 3 from 2016 to 2020, indicating that Democrats may be close to tapped out for now.

IDK, Illinois has such weird politics.

How has the racial composition changed? Wouldn't surprised me if it's gained blacks from Chicago, lost whites to Indiana, had old whites die off, and had the usual Asian and Hispanic population increases.

I think that’s part of it, I believe it’s a higher % Asian and Hispanic than one would expect being often thought of as white and affluent. I do think one of the posters above also had a point about it being in favor of societal norms and trusting of institutions (which lends to being liberal these days) but not so much that they want to  disrupt the economic paradigm they are thriving in (so no economic left wingers). Another factor is probably that it is pretty much entirely suburban. This is a contrast from typical collar counties that extend into rural/exurbs. Kane, another suburban collar county, is pretty much entirely west of it so it houses most of the sparse Chicago western exurbs rather than DuPage. And finally Trump was just a bad fit

[Unelectable Bystander]

Trump was a horrible fit for it.

Bear in mind that it's not really a Gwinnett situation where there was a ton of demographic change because it's barely grown in the past two decades. Downballot Republicans still do far better than Trump, and a non-Trump R should be able to do substantially better. Interestingly, it swung 15 points left between 2012 and 2016 but only 3 from 2016 to 2020, indicating that Democrats may be close to tapped out for now.

IDK, Illinois has such weird politics.

How has the racial composition changed? Wouldn't surprised me if it's gained blacks from Chicago, lost whites to Indiana, had old whites die off, and had the usual Asian and Hispanic population increases.

I think that’s part of it, I believe it’s a higher % Asian and Hispanic than one would expect being often thought of as white and affluent. I do think one of the posters above also had a point about it being in favor of societal norms and trusting of institutions (which lends to being liberal these days) but not so much that they want to  disrupt the economic paradigm they are thriving in (so no economic left wingers). Another factor is probably that it is pretty much entirely suburban. This is a contrast from typical collar counties that extend into rural/exurbs. Kane, another suburban collar county, is pretty much entirely west of it so it houses most of the sparse Chicago western exurbs rather than DuPage. And finally Trump was just a bad fit

Kane is also anchored by Aurora which does cross into Dupage and slightly pushes it left but not much. Overall other than McHenry which is exurban the other collar counties do have defining industrial satellite cities that are more similar to Gary from what I understand than true suburbs of Chicago. Although they haven't suffered the same decline as Gary.

Yes that speaks to why the collar counties are blue in general, since most of them have a small city within them. DuPage has Naperville (which is probably more suburban than city, but still nets a ton of Dem votes I believe) and a small part of Aurora. Kane has Aurora and Elgin, which are both legitimately urban at some points. Someone can correct me if I’m wrong but I think Kane would vote R absent of those two city cores?