My hope would be that the problem isn't "major donors" but rather uneducated and misrepresented citizens. The question about donors or deep states or any other conspiracy type scheme is both how they might affect the purpose of the education system and the integrity of the democratic machinery. These should be questioned, but fixing them might be more achievable than eliminating "major donors" which is certainly tied to income inequality in general, some level of which is most likely desirable.

Major donors have better access to the media than me. I can't educate them if the major donors are spinning opinions. My HN post will reach a negligible proportion of the voters; their prime time ad will reach a huge number.

Vote for better politicians.

Step 1 is to get better politicians to run. Only then can you vote for them.

If in the first election there's no-one worth voting for, stand at the next election.