I would not describe WTA by district as “proportional.” That’s a word people who don’t understand math use to describe WTA by district, e.g. Megyn Kelly.
“Winner-take-most” is a better shorthand for it. It’s very unlikely a state’s districts would be evenly split between two winners. Usually one candidate gets the lion’s share, as Cruz did in Wisconsin. Also often, someone wins them all, as Trump did in S. Carolina.
Thanks. Then California should be considered Winner Takes Most, not proportional.