It is a wonder they don't spend more.

For business people looking for bang for the buck, political contributions represent a sure-fire return on investment. Relatively small amounts invested in the U.S. political process often result in policy changes of enormous consequence to individual companies or entire industries.

This may not be bribery in criminal law terms, but it is something awfully close.

And even the bribery label does not fully capture the systemic and pervasive corrupting influence of money on the political process. Individual examples highlight how crude the quid pro quo may be, but they don't illustrate the broader and profound degradation of the democratic process.

Money first affects who chooses to run for office. At the federal level, running a credible race for the House of Representatives requires at least a half million dollars, and in most cases closer to one million dollars. This de facto requirement tends to filter out those who don't have rich friends or a willingness to consort with, buddy up to and support positions favored by the wealthy. At the same time, it tends to attract to the race those who themselves can invest huge sums in electoral politics, since federal campaign finance limits do not apply to personal spending.

Although there is nothing inevitable about it, money then affects the nature of the campaign. The campaign industry flocks to well-funded candidates, doling out conventional wisdom -- most of it wrong -- about voter preferences on economic questions. (Opinion polls demonstrate the electorate is much more populist-inclined than centrist-obsessed consultants suggest.) Campaign consultants direct candidates to pour their money into television ads (and take a cut of the money spent on TV commercials). The emphasis on TV tends to turn the campaign away from grassroots mobilization -- another bias in favor of corporate interests.

And money does affect outcomes. Those who raise and spend more tend to win, though there is of course not a perfect correspondence between dollars spent and votes won.

Once in office, the payback to major contributors is typically described as "access." Members of Congress return the calls of major donors (often, they're making the calls!) -- something that is certainly not true for most constituents.

But "access" does not capture all the benefits afforded major contributors. Elected officials routinely check with big donors on legislation that would directly affect them. On these matters, votes against their major donors are rare. If a big contributor finds itself hassled by a regulatory agency, it goes to its friends in Congress and looks for help in curtailing regulatory vigor. When a major contributor wants a provision inserted into a tax bill, they know where to turn.

Policy positions on broad national issues are also skewed by political money. Here, politicians tend to follow party positions -- but those positions, set by elected party leadership in the legislature or in the executive branch, are themselves tailored to reflect major contributors' interests.

Money-raising pressures do not diminish on those elected to office. They must devote huge amounts of time to fundraising, a constant reminder of how their performance may affect their cash flow. And time spent cavorting with lobbyists at fundraisers and speaking with the rich colors their worldview.

Things come full circle at the next election. Incumbents tend to be flush with cash -- having worked hard during their term to satisfy donors -- and the incumbents' bankrolls tend to scare off challengers.

The money flows to politicians through multiple channels: individual donations, political action committees, bundled money, "soft money" contributions to parties, contributions to state funds and independent expenditures (not coordinated with campaigns). Blocking one channel tends only to divert money to another, which is why campaign finance reform must be comprehensive to have much effect.

Given existing Supreme Court jurisprudence holding that campaign spending equals speech and is entitled to strong First Amendment protections, public financing schemes represent the best hope for dealing with campaign corruption. The basic structure of most such arrangements involves a substantial public allocation to candidates that foreswear private money, and a promise of matching money if an opponent spends more than the public allocation.

It is important not to overstate the significance of such a reform (which should be carried out at federal, and state and local levels). The money and politics problem would remain: corporations would still spend hundreds of millions on lobbyists; the revolving door would continue to swirl between the public and private sectors; and the schmoozing problem -- of public officials and their appointees and staff spending too much time with lobbyists -- would persist.

More importantly, campaign finance reform would not affect corporations' dominant position on the ideological terrain -- reflecting their power and backed by think tanks, academics on the make (or take) and a corporate-dominated news media -- or their ultimate trump card, the threat to close and move elsewhere if policies do not comport with their demands.

But while not a cure-all, public financing would eliminate one enduring source of corporate leverage and remove some of the corrupting odor which now infects politics in the United States.