This is why, if I was elected god by mistake, I'd make the primaries not more than 90 days in advance of an election. I'd also use a constitutional amendment to limit campaign money to only those who are eligible to vote in the primary for the current election. Ban all campaign ads not run and produced by the candidates, but allow parties to advertise. Hell, if we are going full force on this, I'd make us a Mixed party representation system. CGP Grey explains it here. This solves the Gerrymander issues as well. My hope with this election is that the clowns all blow themselves out in a big puff of wind and hot air allowing the adults in the R and D party step in and put someone not insane in the running. I keep thinking about Clinton in 1992; he was a nobody who came out of left field as far as the public was concerned. He did not even announce he was running until October. Hillary will never be president; at this point she is nothing but baggage, she is too old (IMO) and if she wins the nomination, every right wing nut, every conservative, every "not Hillary" person is going to shovel cash at the R who runs against her. Meanwhile I am going to sit over here and not give money to anyone this year. This will be the first presidential run since adulthood that I don't write a check.
Bartcop came up with the most ingeniously simple idea I've yet heard - if you want federal matching funds or run ads on the public airwaves, you have to give 33% of your donations to your opponent (or opponents - a general fund would be easy to set up). If you had to give one million of your three million to the other guy, you'd still have an advantage... but not a massive one like you have now. He's in the same boat. Of course, this was before the Koch brothers really became a thing, but I've always thought there was a brutal simplicity to it...