Demography Is Political Destiny

None of this is particularly surprising, but it doesn't hurt to note confirming opinions from third-party sources once and a while. The rankings are based upon three demographic considerations:

1) What percentage of the state's residents 25 or older have bachelor's degrees or higher?

2) What percentage of the state's residents are White?

3) How urban or rural is the state? . . . 

[T]he most demographically friendly state for Republicans is ... WEST VIRGINIA!

Yes, the same West Virginia that Sen. Joe Manchin, a Democrat, represents. That should convince any lingering Democratic doubters that the alternative to Manchin in the US Senate is almost certainly a Republican.

Here are the rest of the most GOP-friendly states in the top 10:

2. Wyoming

3. Kentucky

4. (tie) South Dakota, Idaho, North Dakota, Iowa

8. Montana

9. Maine

10. Arkansas

And here are the 10 most Democratic-friendly states:

1. Maryland

2. New Jersey

3. New York

4. California

5. Massachusetts

6. Hawaii

7. (tie) Connecticut, Illinois

9. Virginia

10. Colorado

Notably, the state at the top of the list here, Maryland, is represented by Republican Gov. Larry Hogan.

These rankings generally line up with recent presidential election results. Only two states in the top 10 for Republicans (Iowa and Maine) have voted for a Democratic presidential nominee in the last decade. And none of the 10 most Democratic-friendly states have gone for a Republican in the last decade.

Which state is in the demographic middle? 

Michigan, which ranks 25th. The state has played host to two very close presidential contests, in 2016 (won by Donald Trump) and 2020 (won by Joe Biden).

From CNN, citing the blog of Larry Sabato, a pundit and professor of political science at the University of Virginia. 

The District of Columbia, of course, is the safest Democratic party stronghold of all, although it only has a say in Presidential elections and doesn't have voting representation in Congress.

Reasons for Maine to be an outlier (e.g., it is in very secular leaning New England, where white rural voters are much more likely to favor Democrats than elsewhere) and indeed for most of nine other outliers when considering only the three main demographic factors above (which are all explained to a great extent by strength of religious belief) are easier to articulate than the reason that Iowa is a battleground state in national elections.

Iowa is the 15th least educated, the 6th most white, the 11th most rural, and the 19th most religious state and is tied for 4th most demographically Republican leaning on a composite index of the three demographic factors identified above.