Before I begin, I want to say that I know Connecticut no longer has functioning county governments. However, the old county lines can still be useful because finding the information for all the individual cities and towns would take a lot more time than I have right now. I eventually want to get around to doing city and town information eventually, but for the sake of this series I will keep consistent with the other states.
In 1884, 1888, and 1892 Connecticut voted for Grover Cleveland, the only New England state that went Democratic in those elections. Looking at the county level, around this time there were divisions between the Republican-leaning WASP populations, especially in Yale, and the Democratic-leaning Catholic ethnic populations and state government employees in Hartford. Also some interesting trivia on Cleveland’s family: his grandfather William served in the Connecticut legislature and his father Richard graduated from Yale.
In 1896 Republicans’ fortunes took a sharp turn for the better after Democrats became divided over issues including William Jennings Bryan’s presidential candidacies, as well as who would control the state party, the rural Yankees or the urban Irish. Factory workers voted Republican except Irish Catholics. The rules that called for one town regardless of size to elect one representative also assured Republican dominance. While Connecticut was solidly in the Republican column, its PVI became less Republican due to the national popular vote catching up in the early 1900s.
Unlike the country as a whole, Taft placed second in Connecticut in 1912 so the state was more Republican relative to the country as a whole. The industrialized/Protestant-influenced north outside of Hartford voted more Republican than the Yale/immigrant-influenced south through the Wilson elections. Connecticut’s popular vote followed fairly close to the nation at large in most of the 1920s, as in big Republican wins in both. (Davis in 1924 received similar numbers in Connecticut and the nation at large; Coolidge did better while LaFollette did worse.) The better Republican numbers in 1924 were balanced out by Smith doing better in Connecticut than the nation at large in 1928.
Connecticut didn’t trend as dramatically Democratic in the 1930s; in fact it trended Republican through 1936. Hartford switched to a Democratic PVI in 1940 and stayed that way ever since. New Haven would remain slightly Republican for some elections, but never had a PVI greater than R+2.33 since 1940. New London and Windham Counties in the east were evenly divided from FDR’s 4th term to JFK. Windham County, in the Quiet Corner, is part of the media market of Worcester, Massachusetts, and trended slightly Democratic.
The 1960s saw a dramatic Democratic realignment throughout the state. Only Litchfield and highly wealthy Fairfield, parts of the greater New York area, at the time were at the most swingy. Through the Nixon, Ford, Reagan, and George H.W. Bush years, these two counties were the Republicans’ bases of support. Democrats’ base at that time was Hartford; even New Haven County at this time was still swingy, as were the rural counties to the east.
The 1990s saw eastern Connecticut trend Democratic as the Religious Right’s influence in the Republican Party increased, which likely turned off many secular voters. Western Connecticut also saw Democrats improve their numbers at this time. The Democratic trend continued downballot in the 2000s, when Republican incumbents in the U.S. House were voted out. Even Fairfield, while still leaning Republican PVI-wise, voted for Clinton in 1996 and had stayed with the Democrats ever since. However, in the 2010s, the trend in Eastern Connecticut reversed, with voting patterns similar to the 1980s. Litchfield also returned to being a Republican-leaning county. Hartford and New Haven also saw a slight decrease in Democratic strength but remained strongly Democratic. Fairfield was the only county that trended Democratic in 2016 and is now only less Democratic than Hartford and New Haven.
Here is a link to the Connecticut PVI table.
Here are the maps: