In an earlier case, Buckley v. Valeo, heavily relied upon in Davis, the Court had

soundly rejected a cap on a candidate's expenditure of personal funds to finance campaign speech. We held that a candidate ... has a First Amendment right to engage in the discussion of public issues and vigorously and tirelessly to advocate his own election and that a cap on personal expenditures imposes a substantial, clea[r] and "direc[t]" restraint on that right.

This was a per curiam  decision [generally short and non-controversial decisions issued in the name of the court rather than in the name of specific justices], in which Mr. Justice Stevens took no part; in other respects, it was more or less unanimous. The validity of Buckley was not substantially in question in Davis. Filthy Rich Fat Cat politicians, members of the obnoxious Ruling Elite, therefore were and still are allowed to spend as much as they desire of their own funds on their own political campaigns. The Buckley Court held that diminution of their ability to do so lacks any cognizable public interest.

What was at issue in Davis was rather different. Davis deals with the consequences of those obnoxious fat cats doing so. Under the law held unconstitutional by the five - four Court majority, the consequences are too severe and therefore unconstitutional. The Majority Opinion said,

a candidate who wishes to exercise that right has two choices: abide by a limit on personal expenditures or endure the burden that is placed on that right by the activation of a scheme of discriminatory contribution limits.

What are those discriminatory contribution limits?

Under Section 319 of the Act, when a candidate spends more than $350,000 in personal funds, his opponent may qualify to receive both larger individual contributions than would otherwise be allowed and unlimited coordinated party expenditures. Moreover, Section 319(b) includes substantial rather burdensome and disparate reporting requirements, and failure to comply with them is subject to criminal prosecution.

Perhaps the main point made by the Court in failing to find the necessary public interest in infringing upon the First Amendment is as follows:

Different candidates have different strengths. Some are wealthy; others have wealthy supporters who are willing to make large contributions. Some are celebrities; some have the benefit of a well-known family name. Leveling electoral opportunities means making and implementing judgments about which strengths should be permitted to contribute to the outcome of an election. The Constitution, however, confers upon voters, not Congress, the power to choose the Members of the House of Representatives, Art. I, §2, and it is a dangerous business for Congress to use the election laws to influence the voters' choices.

Here, I think the Court got it right. If Winfred Megabucks III, a Rich Fat Cat (and therefore, of course, a despicable person) with no public name recognition and no membership in the Established Elite Politician's Club, decides to run against a Kennedy or even a Clinton, and cares enough about it to spend his own money, he should not be unduly impeded in his efforts. The electorate can reject him simply because he has too damn much money, or because his views are unpopular, or for whatever reason they choose. And that, in essence is what the Davis Court held.