Not to insult you, Arkinsaw, but everytime I see this point of view expressed on FR, I want to tear my hair out. Why? Because it just screams ignorance of how our political system works.
Parties do not select candidates to run in primaries. Candidates select themselves, partially due to their own ego and belief they can make a difference, and partially due to encouragement from family, friends, and associates.
Parties do not elect candidates in primaries. Voters do.
If you want better candidates in the primaries, you can either: (1) run yourself, (2) find a viable candidate you like, do it well before the primary season begins, and help that person get on the ballot, or (3) if your state has open primaries, get involved and work to return to traditional closed primaries. Other than having a political point of view you agree with, someone is a viable candidate if they can raise funds to run a potentially winning campaign, and if they can craft a message that appeals to a sufficient number of voters.