Easier said than done. I have personal real life experience with exactly that. Do you?
You can't get through the Illinois primary process without the blessings of the GOPe. Now, if you have a LOT of money you could try, but the Party will try to stonewall you just like they're doing to Trump.
Well, excusing yourself from the process is going to lead things in exactly the direction that you are decrying. The politician’s support will be found more and more in the middle, those purist conservatives having long walked away.