I’m not sure how far out early voting began, but perhaps some of the votes were cast before Cruz and Kasich dropped out. If not, then the votes were simply protest votes.
Oregon registered voters.
Democrat 953,070
Independent 109,531
Republican 684,404
Nonpartisan 540,637
(nonaffiliated, minor parties & others)
Early voting doesn’t seem like a great idea, at least to me. So many things can happen.