As for this campaign finance reform proposal, each candidate choosing to participate will be given a certain amount of money. To be able to take part, candidates must be able to collect a certain number of signatures plus small contributions.
Candidates cannot use their own money and accept donations from the outside once public funding is given to them. They can still accept matching funds given that their opponents are benefiting from independent expenditures, they are being attacked directly by independent expenditures, and they are being outspent by candidates that are privately funded.
However, limits will be set as to how much matching funds can be received. Nevertheless, this is why clean money financing systems are preferred over presidential campaign systems because the latter does not provide extra funding for candidates under attack.
Not to mention that Clean Elections levels the playing field, as seen in Arizona during its first year of implementation, with disproportionate funding at just 2% in the electoral races between candidates.