U.S. Senate Republicans conceded defeat Tuesday in the campaign-finance debate and called for immediate passage, likely Wednesday.

The bill is seven years in the making and would severely restrict the use of soft money in campaigns for the U.S. Senate, House and president and could encourage lawmakers in Wisconsin to reconsider campaign-finance legislation.

“It’s time to bring this to a conclusion,” declared Senate Minority Leader Trent Lott, R-Miss.

Lott asked for a vote Tuesday but was unable to gain the necessary votes from Democrats.

Republican opponents of the bill, led by Sen. Mitch McConnell, R-Ky., conceded they no longer have the 40 votes necessary to sustain a filibuster in opposition to the bill.

Senate Majority Leader Tom Daschle, D-S.D., filed a petition to force the vote by Wednesday, potentially forcing the Senate to remain in session well into the night to hammer out a piece of legislation.

The bill, approved in a different form last month by the House, would ban unlimited “soft money” contributions to national political parties and restrict such contributions to state and local party affiliates. It would restrict issue advertisements currently utilized by third-party groups to target candidates before elections.

Jay Heck, executive director of Common Cause in Wisconsin, said soft money currently being used in campaigning is a loophole in the law.

The ban of soft money would weaken the influence of special-interest groups in elections and public-policy decisions.

Bush, who opposes some key elements of the bill, has not publicly specified whether he will sign the bill, although Democratic and Republican leaders said they expect him to sign it.

Heck said the bill would end the use of soft money.

“This will end the corrupt use of soft money,” Heck said. “This unregulated, unlimited, unrestricted cash was never supposed to be used.”

The ban on soft money, Heck said, would eliminate nearly $500,000 in campaign funding.

The legislation, if passed in current form, would not take effect until after November’s midterm congressional elections.

UW-Madison political science professor Charles Franklin said he believes the bill has a good chance for passage.

“I think it is likely to pass at this point,” he said. “Even Mitch McConnell, the main opponent in the Senate who looked like he might filibuster or otherwise block it, seems to be admitting defeat. However, it may be another ploy to kill the bill. But this time, Enron contributions are an issue that was not there before. Neither was House passage.”

McConnell admitted the fight over the bill had ended.

“We look forward to wrapping up this bill tomorrow,” McConnell said. “We know it is essentially over.”

Despite Republicans’ admittance the fight is over, they have already begun preparing to challenge the constitutionality of the bill.

Daschle threatened to hold all-night sessions if action were not taken on the legislation, but McConnell said Tuesday this was not necessary because everyone is prepared to move on the legislation.

“There is no necessity to have all-night sessions since the opponents of this bill are ready to move on with it.”

–Reuters contributed to this report.