Here's a quick and simple campaign finance reform - Require that any contributions to a candidate MUST designate THAT CANDIDATE and THAT ONE CAMPAIGN as the ONLY permissible beneficiary of that money. The donor would indicate on, and at the donation, for whom it was intended and for which one campaign it is to be used.
Candidates could raise as much as they want in this manner, without limit, but any excess funds (after all expenses and debts are extinguished) could NOT be used in any other campaign, even a later one by the same candidate. Maybe, by rule, any excess that did remain would need to be donated within a specific time period, e.g., 3-4 months after the campaign ends, to some well known charitable concern(s), perhaps from an approved list.
This would prevent the most popular (or controversial) candidates amassing huge war chests and then acting as sugar-daddies to other candidates in their party, or perhaps using the funds themselves to finance an early start on their next campaign, e.g., a run at their party's Presidential nomination. In fact, it would eliminate the rationale for raising excessive funds in the first place, certainly something "devoutly to be wished".
Because donors would not see their $$ used at a different time and place - to say nothing of it being used for a different politician - than they'd originally intended, this reform would reflect the "will of the people" much better. And think of the many positive ripple effects. First of all, in some races, probably much less fund raising would be needed because so much less could be used. Second, what would occur would be distributed much more broadly, i.e., far less concentrated in terms of who controls that money. And, it would be much more targeted based on the "will of the people", or at least on the will of the donors. Of course, funds donated to a political party could not be limited as to the candidate who benefits, but at least the campaign season could be limited to the current one, so there'd be no carry-overs allowed into a later years' campaign.
In as much as money is free speech, as the Supreme Court has told us, this form of free speech would suddenly be a far more accurate reflection of the public will. But, alas, many ideas (at least, many of mine) are both good and, realistically speaking, thoroughly hopeless of enactment. This is just one more.