[Resettozero]

Closed primaries are the way to go.

That sounds like the easy fix but how would non-Republicans be excluded from registering as Republicans, which is what they do now?

[GenXteacher]

No system is perfect- but usually the offenders will want to vote in the Democratic primaries too. It is a bit inconvenient to switch parties constantly if you have to keep changing your registration, so it slows the left-turn effect down.

[cripplecreek]

The problem is that democrats will just accept any candidate their party chooses and cross the line to manipulate the republican race.