Illinois will NOT trend heavily Republican

[Southern Senator North Carolina Yankee]

IT is not that under current factors that it will trend Republican, but it could rapidly trend Republican once the Republicans are locked out of the electoral college due to demographic changes in sunbelt states.

The very changes needed to stay competitive there, would make them more acceptable here. Likewise, the changes needed to regain a path to winning after losing those states has the same effect.

It stands to reason that Republicans would have a strong base of support in Illinois, even if deep in the minority and thus makes it a likely hot spot for Republicans to craft a winning message that can get them the President back in the late 2020's or early 2030's. It is also still going to be less diverse than CA, TX, FL and NY.

[Southern Senator North Carolina Yankee]

Yeah these things all come down to whether polarization will linger on or not.  If so, perhaps not.  If not, then you might as well put all the states in a grab bag, considering how wildly the electoral map swung around during the New Deal era.

Even in a polarized environment states shift over time. Like in 1904 when TR won Missouri, which previously had almost always voted with the former Confederacy. You still had polarization in that the North voted Republican, South voted Democratic, but Missouri had become a Midwest state with the growth of St. Louis. Now the state has become more Republican partially because St. Louis has declined significantly. I think the most unrealistic of projections of was those that foresaw the 2004 map existing forever. We have since seen VA and CO become Democratic states.

I do think that regardless of whether or not polarization ebbs, it will decline in terms of the current divisions and at the very least shift to a new set of dividing lines.

[Southern Senator North Carolina Yankee]

I never disagreed that the GOP needs to become "more suburban", my main disagreement is that I think the Republicans need to do that by becoming more focused on an economic message that actually benefits most people who live in suburbia, not the fictional cast that elites like to think inhabit them.

The Republican losses among the suburbs are not driven by trade, or frankly even immigration It is the simple fact that Republican no longer have the golden economic key to their economic interest that made them Republicans, regardless of all other issues. Remember these are some of the same white flight suburbs who largely stuck with Goldwater compared to other places. 

The economic interests have shifted and the Republican's purist direction on economics has gone the other direction. Which has in turn, made the purist direction on social issues since the 1990's just that more salient and damaging. To the extent that trade motivates some lower middle class outer suburban or exurban resident to vote Republican, is a good thing relative to say trying to use taxes to leverage the children of tax conscious Reagan voters, who are far more concerned about a mountain of student debt, lack of wage increases, climate change and equality issues.