Washington ? It was a famous victory. The campaign finance bill now has passed both the House and Senate and likely will become law with President Bush’s signature.

The bill has one great virtue. It will end the ugly and indefensible practice of federal elected officials extorting six-figure contributions to their political parties from corporations, unions and wealthy individuals. It is clear and definitive about doing that, and it will be effective.

Beyond that, the consequences of the bill the Senate approved last year and the House passed early Thursday morning are probably not what supporters have been led to believe. The optimism of the backers is exceeded only by the folly of the House Republican leadership, who must be grateful today that the Olympics captured the TV audience from C-SPAN, so relatively few people saw the string of fraudulent Republican amendments so nakedly intended to kill the bill. Their tactics give hypocrisy a bad name.

Still, parts of the bill are probably unconstitutional, and other parts largely unworkable or unenforceable. As with previous campaign finance legislation, it is likely to have big unintended consequences.

For example, the Democrats who furnished the bulk of the votes for passage may be dismayed to learn that in the view of Michael Malbin, the widely experienced head of the nonpartisan Campaign Finance Institute, the bill hands President Bush an enormous advantage in his 2004 re-election campaign.

Here’s why: In 2000, when Bush rejected public financing of his race for the Republican nomination, he assembled a record treasury of “hard money” contributions (limited to $1,000 per person) from family friends, Texas supporters and allies in the business world. As an incumbent president, he can probably double or triple his take, while at the same time avoiding the spending limits that go with public financing.

No Democratic challenger is likely to be in a position to reject the taxpayer subsidies, and in a serious contest, on the accelerated calendar Democrats recently adopted, all the Democrats may well hit their spending limit by mid-March. In the past, the winner could turn to the Democratic National Committee and ask it to finance waves of TV ads from its “soft money” account at least until August, when the convention formally made him the nominee and a Treasury check for the autumn campaign arrived.

If this bill becomes law, Malbin points out, the Democrats will have no federal soft money account; their nominee may well be off the air and invisible for five months while Bush dominates the political debate.

Another unintended consequence may well be to shift the flow of “soft money” from national parties to state and local parties. Contrary to the impression left by many editorials, this bill does not make all “soft money” contributions illegal. The amendment sponsored by Michigan Democratic Sen. Carl Levin allows state and local parties to receive up to $10,000 a year ($20,000 per election cycle) in individual “soft money” contributions, as long as they do not spend it on ads for federal candidates.

Theoretically, one wealthy individual could drop $1 million or more into his favorite party, by writing separate checks to 50 state or local party headquarters.

You can call this a giant loophole or a wise provision to support grass-roots activity, but it goes against the centralizing forces in our politics which have strengthened not just recent presidents but congressional leaders of both parties.

When the national parties do less for their presidential nominees and their congressional candidates, those men and women become even more individual political entrepreneurs.

It is perhaps not a coincidence that all four of the sponsors Sens. John McCain and Russ Feingold, Reps. Chris Shays and Marty Meehan are notable for their maverick tendencies. It is likely this legislation will breed more of their kind.

Finally, the issue the opponents of this bill tried without success to raise is its impact on the relative power of interest groups and political parties. The most dubious parts of the measure are those regulating “issue ads” that non-party groups run during election campaigns. These provisions implicate basic First Amendment rights of expression, and if the courts find them unconstitutional, then the net effect may well be to empower interest groups, while restricting the parties’ participation in campaigns.

Interest groups are as American as apple pie. But their agendas are, by definition, narrower than those of the broad coalitions called Republicans and Democrats. It will not help our politics to magnify the power of narrow interests at the expense of the two-party system.

David Broder is a columnist for Washington Post Writers Group.