Replace First-past-the-post voting at the state level. Give republicans a chance to vote for another political party. Give the voters more then one chance to defeat the republicans.

Oh and free and fair elections for all should be a purity test everyone passes.

But this is all stuff that should have happened 40 years ago. So realistically the correct answer is massive pain and loss. Pain so great, people wont be afraid anymore because they have nothing to lose.