Theoretically?
You turn the voter base against such politicians. Make it more difficult for them to be re-elected. Make them know that their meal ticket is your ballot. You attack weak seats and elect your people to occupy them, and then form an additional coalition on the legislative level that energizes the electorate on a broader scale-- both those things make it more difficult for the establishment types to disenfranchise you because if you all go, you're leaving seats that can be taken by the opposition and you take those aligned with your base with you.
You become a grunt in their organizations and ingratiate yourself with them, rising through their ranks silently until you're in a position where something can be done, and then you steadily start doing what you can where you are while leaving room for additional advancement if need be.
You pool resources and create PACs or at least simple money pools to support your people.
You polish your PR so that you can maximize the suspicion people have when you're maligned by the opposition.
There's always ways to push back-- things get sticky when you talk practicality.
Turning the voter base against an established politician who needs to be pruned is risky when you don't have a capable and captivating candidate-- unless you can cultivate desperation or hope, people will vote for the familiar. Should Trump be definitively defeated, that can shock plenty of people to go back to voting familiar instead of vying for what they recently lost-- this isn't them acting out of desperation, but out of resignation, since they can't let "the other side" win.
Advancing this way also requires coordination, because you have to operate clandestinely, if only initially. If you want to take seats, you have to coordinate to take low profile seats first and changing what you can there (so no gunning for Cocaine Mitch's skull throne from the jump). We're talking state delegations "small"-- in fact, even smaller than that, like county/city council seats.
And whether we talk about claiming legislative seats of any kind or ingratiating yourself with the establishment orgs, since you have to be subtle, one runs the risk of being corrupted by apathy (loss of hope in the face of the political machine) or an active selling of soul (pressure is put on you to say and do the """right""" things). On the opposite side of concern, you can have the undisciplined completely blow their power levels and get shitcanned in short order (to say nothing of payment processors).
What's certain is that this takes time, coordination, discipline, clarity-of-vision, and patience. If you start this coalition, you cast your vision in stone, and you permanently establish a sense of conduct that defines how you engage with the in-group and out-group. You wait until you've amassed enough influence before you make big moves. Casting broad nets is good, but everyone needs to know the score so nothing gets derailed by white nationalists/supremacists/identitarians or any other group who doesn't have a snowball's chance in Hell to get anything of value done except allow your group to be much more easily maligned.
Of course... it's becoming all but certain that the Right-- in general-- has its work cut out for it in the next 0-4 years, to say nothing of the demoralization left in the wake of a Trump loss under suspicious circumstances.