Unregulated campaign cash from special interests is rolling in, the first wave of "attack ads" are flickering across television screens, and Congress today will begin its annual debate over what--if anything--to do about it.

Despite money scandals from the 1996 campaign and signs that fund-raising for next year's elections will set new records, the early outlook is for a repeat of last year, when the House passed a bipartisan bill reining in fundraising, only to see it killed by a Republican filibuster in the Senate.

But the issue of changing campaign finance law is a volatile one, and the bill's sponsors argue that voters are increasingly restive over the growth of special interest influence on elections. Reform advocates have gained some ground in recent years, including achieving a majority in both houses, although falling short of the 60 votes needed to pass the measure in the Senate.

So there is enough doubt about the outcome in both chambers, starting with a series of votes on "killer" amendments in the House today, to keep both camps on edge.

The heart of the legislation, sponsored in the House by Reps. Christopher Shays (R-Conn.) and Martin T. Meehan (D-Mass.), is a ban on "soft money" that corporations, unions and wealthy individuals give to political parties without having to abide by contribution limits and other rules that usually apply to donations to federal candidates.

This unregulated money, ostensibly for party-building activities, is used increasingly by both parties to promote their candidates. It was the focus of inquiries into 1996 funding abuses. National party committees raised more than $55 million in "soft money" in the first six months of this year, compared with $30.6 million in the same period four years ago, according to Common Cause, which supports the legislation. Republicans have an advantage over Democrats in collecting such funds, and party leaders have warned that passage of the bill could erode that advantage.

The Shays-Meehan bill would also apply contribution limits and other regulations to campaign-season issue advertising that is clearly aimed at electing or defeating a specific candidate. Many such ads now escape regulation by attacking or praising candidates without directly urging people to vote for or against them.

The Senate bill, sponsored by Sens. John McCain (R-Ariz.) and Russell D. Feingold (D-Wis.), is nearly identical, although it may be scaled back or otherwise changed to pick up more Republican votes.

In recent meetings with reporters, Shays and Meehan indicated cautious optimism about their prospects in the House, where they won last year, 252 to 179. But they also signaled unease in light of behind-the-scenes opposition from GOP leaders and the appealing sound of some of the proposed alternatives and amendments.

Ironically, they said, they do not have the advantage they had last year when then-speaker Newt Gingrich (R-Ga.) created a backlash by heavy-handed tactics to avoid votes on the measure. This year, Shays noted, GOP leaders are "killing us with kindness," even as they continue to oppose the bill.

Before voting on the bill, the House will consider three alternatives and 10 amendments. Among the most serious threats to the bill is a popular and non-controversial alternative from Rep. William M. Thomas (R-Calif.) to beef up the FEC. Shays and Meehan are fighting it on grounds that it would kill their proposal and say they will incorporate its provisions in their bill when allowed to under the rules.

Many of the amendments are similar to those considered and defeated last year. Seven of the 10 are regarded by Shays and Meehan as "poison pills" because they would gut their bill or shatter the coalition supporting it. Among these are proposals to increase contribution limits for federal candidates, restrict labor union spending on politics and allow unrestricted advertising on the Internet. New proposals include one that appears aimed at forcing Hillary Rodham Clinton to pay the full costs of government travel to New York while she prepares for a Senate campaign there.

Shays and Meehan see even more problems in the Senate, warning that a single vote on ending the anticipated GOP filibuster will not be enough. In agreeing to schedule action by mid-October, Majority Leader Trent Lott (R-Miss.) insisted on barring further votes this year and McCain went along, although Democrats balked.

Senate backers must be prepared to force vote after vote, just as civil rights supporters did in the 1960s, Shays and Meehan argued. "If they [opponents] know it's just one vote, they'll endure the pain," Shays said. "If they think there'll be 20 votes, I think it [the bill] will pass the Senate."