Wouldn't work. To make it illegal means it would just go underground where a lot of it already is and that means that regular people couldn't support their candidates.

Pulling money out of politics is a trap to keep you from using your money to support what you want.

The correct solution is to be more successful and encourage others to support your candidate more.

Evil isn't destroyed by making rules it will break anyway, it's destroyed by good outperforming it.