An open primary is a type of election where voters can choose which political party's primary they want to participate in, regardless of their own political affiliation. Full definition
In open primary states it's even harder to say that, but when you vote in a primary you're participating in an analogue to a convention, just with many fewer requirements. (politics.stackexchange.com)
He supports open primaries for all special elections, rather than relying on party bosses in «smoke - filled rooms» to pick candidates for statewide office. (thelodownny.com)
Every single constituency must be subjected to a fully open primary election. (conservativehome.blogs.com)