You can't limit campaign finance without trampling the 1st amendment, initiating something very much like a police state.

For example...   If a network devotes 100 hours per week vilifying one candidate while honoring his opponent,  how much is that worth?  How would you stop it?

If a union mobilizes 10,000 members to campaign for a candidate,  how much s that worth?   How would you control it?

The only campaign finance reform that comes close to being fair is an accurate and easily accessible accounting of the source of campaign finance. 

If people chose to be informed, and sadly most don't, that will be the most effective "campaign finance reform".  

In Canada we have equal time allocated for every party on natn'l TV which is free time for each of the parties

If a party wishes to buy additional TV time, that cost counts against their limit on total caimpaign limit

Fortunately or maybe otherwise, we are not a large enough country to mobilize large union members to get out the vote or working for free. Our teachers union is our largest union that I know of and they can be a formidable influence if they wish

However, our country is so diverse that different union members in different parts of the country have different issues, thus have a hard time to be a collective voice for one party

I know union leaders have supported one party but when it comes time for the ballot box the fact of private vote has proven that members will mostly vote their own wish and not listen to the union leaders

In Canada we have more diverse issues such as thoughts on Tar Sand movement to market by rail or some other means

The east coast is vested in fishing rights, while Britsh Columbia may want to protect our natn;l forest

Thus with caimpaign limits it becomes an issue based election vs money spent on TV ads as nobody has enough money to blanket the country with TV ads

Our various party caimpaign expenses are reimbursed to a large extent by Federal re-imbursements, after a financial accounting has been submitted for re-imbursement

In Canada an election PAC is not even heard of or even understood. This money would count for the caimpaign limit

Some how we have managed to account for all money spent on every party caimpaign so it can be done, especially if the amount is small on a per capita basis

Maybe it is because we are 1/10 your size or about the size of Ca. but we seem to make it work. We also have very simple rules limiting spending, which seems to allow us to do the accounting. We can at least make that work, so it is possible

We don't have constitutional problems but I have heard voices from your country thinking caimpaign finance needs  something changed, so they must have considered the constitutional aspect of the problem

I don't pretend to understand your constitutional issues, but most other problems raised sound to me as just excuses why change won't work.

I admit it would be an uphill battle as I have heard various people want change and every time change has not happened.

Your congress has a vested interest in lobbyists and other caimpaign finance

Like how else do you get to be a millionaire unless the rules can be gamed to the advantage of elected officials lining their pocket

Heck even Bernie made millions, owns 3 homes, has a portfolio of capatilist fortune 500 Co's and never had a job in his life