If Rep. Christopher Shays can rally 60 fellow Republicans in the House to pass serious campaign-finance reform, Sen. John McCain can get the additional half dozen senators he needs to override a filibuster and take this rare chance to get reform into law. But there is little time to do it.

The House earlier this month passed, 252-179, legislation by Reps. Shays and Democrat Martin Meehan. The bill had been batted about, amended and rewritten before being approved, but had kept its key provision: the banning of soft money. That’s the channel that national parties use to raise and spend money on individual candidates. The parties haul in the big bucks from special interests because candidates are not allowed to raise these dollars for themselves.

It could not have been easy for House Republicans to defy the wishes of leadership and help stop the obscene amount of money that flows into campaigns. Particularly in a year in which leadership has seemed determined to allow as little as possible to happen, the major breakthrough on campaign-finance reform was remarkable, and they deserve credit.

Now, it’s the Senate’s turn, where the outcome of this popular measure is uncertain. Supporters can either try to attach their version of the bill to major legislation to get it passed or attract enough Republicans — Democrats already support it — to beat a filibuster. The last count of supporters was at 54; 60 are needed to override the filibuster. But a switch of even two or three senators could be enough to force several others to join — or risk being caught on the wrong side in this vote.

Ten of New England’s 12 senators — including Olympia Snowe and Susan Collins — are likely supporters of one version or another of the reform. New Hampshire Sens. Judd Gregg and Robert Smith remain opposed. The GOP traditionally has fought the soft-money ban because it gained more from the cash source than Democrats did. But President Clinton’s talents for indiscriminate fund raising in 1996 shows this may no longer be the case. The chance that the two parties would be equally reined in by the reform makes this an excellent time to pass it.

First, however, senators must be as dogged about insisting on a vote during the few weeks they will be in session, starting in September. Senate leaders will try to delay debate on campaign finance until adjournment. Supporters’ weapon against this is to threaten to attach the legislation to spending bills that either pass or bring the Senate to a standstill.

That’s not the best way to go about governing, but it beats allowing the corrupted campaign-finance system to continue.