Washington ? Advocates of overhauling campaign finance laws appeared to close in on a key victory today as the House tangled over legislation that supporters touted as a way to reduce money’s role in politics.

As debate continued into the early morning, proponents mostly Democrats joined by a few Republicans bucking their party leadership defeated several attempts to change or kill the legislation.

At the center of the debate was a bill to ban “soft money,” the millions of dollars in unlimited, unregulated donations to national political parties each year by individuals, labor unions and corporations. The legislation would impose the biggest changes in the nation’s campaign finance system in more than 25 years.

If the bill passes the House, it would have to win approval in the Senate, which already has passed a similar measure, and be signed into law by President Bush.

“I want to sign a bill that improves the system,” Bush said Wednesday.

The bill’s backers said they were worried about an amendment that would require the legislation to take effect today. Although Bush has called for such a step, backers say it would strip away the support of some lawmakers who plan to vote for the bill as long as they can complete the 2002 elections under the current system.

Backers, who said their bill gained new life with the scandal over the bankruptcy of Enron, a big political donor, said the legislation would reduce what they believe is the corrupting influence of special interest money in politics. Large contributions, at times $100,000 or more from an individual, leave politicians beholden to wealthy donors and drown out the voices of average Americans, they say.

Lawmakers have “a historic opportunity to end the influence of big money on public policy,” said Rep. Jim Turner, D-Tex., who was instrumental in forcing the bill to the floor against the wishes of House GOP leaders.

“The moment of truth has come,” said Rep. Martin Meehan, D-Mass., chief sponsor of the bill, along with Rep. Christopher Shays, R-Conn. “Members of the House finally have an opportunity to say enough is enough. … Saying you are for reform is easy, but actually being for reform, that’s the part that’s difficult.”

Opponents said the bill was misguided. Money will always find a way into the election system, they said, and the bill’s main effect will be to impose an unconstitutional limit on free speech. They objected not only to the soft money ban, but also to a provision that would prohibition on some political ads on TV within 60 days of a general election.

“This bill doesn’t contain real reform,” said House Majority Whip Tom DeLay, R-Texas. “Instead this bill rips citizens of their political rights and unconstitutionally tries to regulate political speech. … Political speech is the key to political freedom.”