I've always thought it's interesting how the partisan composition in Hawaii on each island runs so closely together. In terms of the share of primary ballots that were Democratic, the 4 islands were individually between 87% (Oahu) and 90% (Kauai); Hawaii and Maui were 89%.
The 2012 presidential was probably the biggest gap recently; Oahu was 69% and the other 3 counties were 74%. In 2016, they ranged between 61-64%.
Any stats for Molokai and Lanai? They're part of Maui (not counting the former leper colony).