We have something like this in Australia. Candidates receive a fixed amount, maybe $2.50, per first preference vote, provided that they achieve more than 4% of all votes.

The 4% requirement avoids creating an incentive for every idiot to register a political party so they can get a few hundred dollars from the Electoral Commission.

The effect is to essentially tie what you proposed into the election itself.

We do still have private donations, but I think they’re somewhat restrictive, and the public funding lessens the benefit of private donations.