Complex sentence: Some of this was due to the state extension of suffrage to women; for example, in Illinois where the total vote was 1,000,000 greater than in 1912, in Kansas where it increased by more than 260,000, and in Montana where it more than doubled.
Split into simpler sentences: Some of this was due to the state extension of suffrage to women. It increased by more than 260,000 in Kansas, and in Montana, it more than doubled.