Campaign finance reform is coming up for a House vote Wednesday after 218 members — a House majority — signed a petition in favor of holding a vote. But some of the people who signed that petition may very well end up voting to kill reform in the end.

They include Democrats like Corrine Brown of Florida, a member of the Congressional Black Caucus, whose members make up a small but critical voting block among House Democrats and who think campaign finance reform will hurt them politically by preventing get-out-the-vote drives crucial in minority communities.

All sides in the debate on campaign finance reform expect something to pass this week, but nobody knows what because there is going to be a free-for-all of counter-proposals and amendments.

The original legislation coming to the floor contains several provisions, including a ban on soft money — the unlimited donations to political parties from special interest groups; virtual elimination of third-party ads in the closing days of a campaign; and increased caps on hard money donations direct to candidates from individuals.

Supporters were cautiously optimistic.

"I believe very much that the momentum is on our side with a lot of hard work to be done," said Rep. Mark Udall, D-N.M., at a news conference Monday where business executives underscored their support for the bill.

"Never try to predict, especially when you're talking about the future," joked Sen. John McCain, R-Ariz., a phrase he attributed to former baseball player Yogi Berra. "I think this is very close. I think we have significant obstacles ahead."

While critics contend the measure violates constitutional free speech rights, primary obstacles to passage are political. Sen. Mitch McConnell, R-Ky., a vocal opponent, said the bill as drafted contains "special Democratic fixes" that would aid the party's drive to construct a new headquarters building and benefit labor unions.

Other obstacles come from GOP leaders, who say they would prefer to limit soft money but not ban it. Other Republicans argue that if they are going to ban soft money for national parties, then it should be banned for state and local parties.

Some opposition comes from the National Association of Broadcasters, which opposes the provision requiring broadcasters to sell time to political advertisers at the lowest advertising rate of the previous six months.

Paid political ads produced about $770 million in revenues for television and radio stations in 2000. Advertisers complained that broadcasters often raise their rates virtually overnight without advance notice, but the NAB said the provision is a "slippery slope toward mandatory free [air] time." An amendment was expected on the House floor to change or delete it.

Actual debate on the Shays-Meehan bill, named after sponsors Reps. Chris Shays, R-Conn., and Marty Meehan, D-Mass., will begin on Wednesday, though representatives are expected to vote on the ground rules for debate on Tuesday.

But even if Shays-Meehan passes, it is very different than a Senate version of campaign finance sponsored by McCain and Wisconsin Democrat Russ Feingold that passed last year. If supporters can amend the bill to match the Senate version, than they can send the bill directly to the president for his signature. Otherwise, any differences between the House and Senate would force them to go to conference to work out differences and supporters say that would create another opportunity for the bill to be killed. The White House said it hasn't seen the final bill so is unprepared to say whether the president will sign or veto it.

Three alternatives will be offered for consideration:

The first alternative will be from House Majority Leader Dick Armey, R-Texas. Armey's office was not releasing exact details of the bill Monday.

The second alternative is a bipartisan offer from Ohio Republican Bob Ney and Maryland Democrat Albert Wynn. Instead of banning soft money contributions, it would cap them at $75,000, the limit set in the original bill for contributions by individuals to parties and political action committees.

The last alternative will be the revised McCain-Feingold bill that passed the Senate.

McCain said he's conscious of the challenges, including one by opponents that threaten to challenge the bill in the Supreme Court if it passes, but he hopes it will pass despite opposition.

"When the speaker of the house says it's Armageddon, then obviously all stops are being pulled out in order to try to defeat this measure," he said.

House Speaker Dennis Hastert, R-Ill., told fellow Republicans last week that the bill could doom their hold on power in the House. Hastert traveled to the White House later in the week to appeal for President Bush's support in changing the measure, but administration officials said they made no firm commitment.

On Tuesday, White House spokesman Ari Fleischer said Bush will not lobby on campaign finance legislation despite a Republican National Committee memo urging GOP lawmakers to keep Bush's views in mind.

The legislation "partially represents the president's views," Fleischer said. "We'll have to see exactly what emerges from the House."

One compromise that may be acceptable is to postpone implementation of the bill until after the 2002 election. The bill as written is supposed to go into effect 20 days after it is signed into law, but McCain said he would be willing to consider a delay.

Fox News' Carl Cameron and The Associated Press contributed to this report.