People often talk about polarization. How America used to be good and bipartisan, with Democrats like Strom Thurmond and Republicans like Jacob Javits. Notwithstanding the fact that Thurmond was a bigot and terrible human being, these claims are somewhat true and somewhat not.
What is indisputable, however, is that THE STATES THEMSELVES have gotten much more polarized than they were in, say, 1988.
I'm going to use snapshot PVIs (over one election, rather than two) and then adjust for home-state effect:
Presidential candidate from your state equals +5 points PVI (Obama only +3 since he had no effect outside the Chicago area)
Vice Presidential candidate from your state equals +2 points PVI
So which states have moved the most leftward? Here's the states that have moved at least 3 points to the left since 1988, in order.
New Hampshire
Vermont
Nevada
Delaware
Maine
California
New Jersey
Virginia
Hawaii (I counted a five point Obama home state effect here as well)
Maryland
Massachusetts
Michigan
Arizona
Florida
Illinois
Connecticut
New Mexico
New York
What do you notice about these states? Three, at best, would go to a Republican in a neutral year: Arizona, Florida, and New Hampshire.
Now let's examine the states that moved at least three points rightward since 1988:
West Virginia
Oklahoma
Wyoming
Louisiana
Arkansas
Kentucky
Alabama
Idaho
South Dakota
Kansas
Iowa
Tennessee
Alaska
Minnesota
Montana
Missouri
Texas
Utah
Nebraska
North Dakota
Mississippi
Oregon
Wisconsin
What do you notice about these states? At best, four would go Democratic in a neutral year: Wisconsin, Oregon, Minnesota, and Iowa.
Now if that's not polarization, what is?
83% of states that have trended in a direction, whether left or right, since 1988 lean in the direction they have trended
That is 34 out of 41 states.
If these states continue their trends (and they won't all continue it: Oregon's not gonna be a swing state soon, and I'm not sure Michigan's gonna remain a blue state too much longer), America will continue to be more polarized. And how many of these states are going to trend the opposite of how they've been going? Probably only the two I mentioned, with Utah and Texas slowly trending leftward but not enough to matter for a long time and Massachusetts slowly trending rightward but not enough to matter for a long time.
Basically, our states will continue to become more and more polarized, and there's not much we can do about it. And maybe THE REASON OUR SENATE IS MORE POLARIZED is because our states are more polarized as well, so more of them have safe seats. In the same way gerrymandering creates safe seats in House districts, so does polarization in Senate seats
Just as a fun fact: who can name the twelve counties that have gotten the most redder between 1988 and 2008 and the six counties that have gotten the most bluer?