THEY JOINED hands to call for campaign finance reform, but Bill Bradley and John McCain understand exactly how to prosper under the current system. The latest disclosures from the candidates show that Mr. Bradley raised $8 million in the past three months, twice the amount raised by Al Gore, his rival for the Democratic nomination. On the Republican side, Mr. McCain raised $6.1 million, nearly as much as was collected by the front-runner, George Bush.

There is nothing dishonorable about these achievements: Messrs. Bradley and McCain are right to favor campaign reform and right to compete wholeheartedly under the existing rules until those rules are changed. Still, it is worth reflecting on the lesson of their money raising. By raising large sums, even in a tainted system, they have been able to compete.

Six months ago, the presidential primaries looked as though they might be colorless. The front-runners seemed sure to enjoy a money-raising advantage large enough to crush competition; secure atop their bulldozers, they would utter poll-tested platitudes and avoid genuine debate. But Mr. Bradley's recent cash intake has erased Mr. Gore's money advantage, and Mr. McCain is rich enough to compete credibly, at least in the early states.

Moreover, this unexpected competition is producing an abundance of debating. Republicans and Democrats have each met three times already and are set for more face-offs before the New Hampshire primary on Feb. 1. Some of the debates have, admittedly, been disappointing. The candidates pretend that the illusory budget surplus can pay for their vote-winning programs; they duck hard issues such as entitlement reform. But the policy discussion has been enriched in at least one respect: Extension of health coverage to the 45 million uninsured Americans is back on the agenda for the first time in half a decade.

In sum, politics remains unpredictable and interesting. And yet, lurking around the corner is the possibility that unregulated flows of campaign money will reduce Campaign 2000 to a charade. Three months from now, when the primaries are finished, it is likely that the Democratic nominee -- whether it is Mr. Gore or Mr. Bradley -- will be left with a nearly empty coffer. If the Republicans nominate Mr. Bush, however, he probably will have lots of cash left over: He has raised about $65 million, a total that dwarfs the war chest of any other candidate. Once the retail campaigning of the primaries is over, this money difference may prove decisive. It will take a lot more welcome unpredictability before voters can bury the suspicion that democracy has been bought.