Negotiations to allow for an up-or-down vote on a constitutional amendment that would ban same-sex marriages collapsed Monday under the weight of election-year politics, setting up a procedural showdown on the issue later in the week.

Republicans rebuffed a second Democratic overture to allow for a clean vote on the legislation, because they argued it would prevent them from offering amendments during the debate. Last night, Senate Majority Leader Bill Frist (R-Tenn.) filed cloture, which will result in the Senate holding a procedural vote on the issue Wednesday — the only vote of record on banning same-sex marriage likely to occur this year.

Senate Minority Leader Tom Daschle (D-S.D.) chastised the GOP leadership for failing to convince their rank-and-file Members to accept their offer to vote on an issue that Republicans have been promoting for several months.

“I hear all these charges of obstructionism,” Daschle said in an early evening floor speech. “The obstructionism oftentimes is on the other side. They can’t get their act together and that’s clearly the case here.”

With the Senate aiming for a single procedural vote on the issue, Sens. John Kerry (Mass.) and John Edwards (N.C.), the presumptive Democratic presidential and vice presidential nominees, will skip the vote to remain on the campaign trail.

“Neither one of them will be returning for procedural votes but they are prepared to return for a vote on a final passage,” said Andy Davis, a spokesman for Kerry.

Republicans had hoped to put Kerry and Edwards on the record as opposing the constitutional amendment even though the two men have publicly declared their opposition to same-sex marriage. But GOP strategists last night said they would seek to link the two Senators’ absence from the debate as evidence they opposed the measure.

“At this point if you are not here for the procedural vote to allow for the debate to go forward you are blocking the bill,” a GOP leadership aide said. “Your absence is a vote on substance.”

Amy Call, a spokeswoman for Frist, said the Majority Leader would attempt to revisit the negotiations today, but signaled it is still his goal to see the Senate cast votes on the bill and at least one amendment.

“We would like to get an agreement to move forward with up-or-down votes,” Call said.

But Minority Whip Harry Reid (D-Nev.) said Democrats preferred to keep the bill free of amendments so that it does not get confused with other legislative proposals.

“Everyone knows if that happens, this amendment would be bogged down with Christmas tree-like ornaments called amendments,” Reid said.

Sen. Sam Brownback (R-Kan.) said Frist was correct for opposing the Democratic offer, saying it was wrong to restrict amendments on an issue of such significance.

“Why shouldn’t we have a full amendment process?” Brownback asked. “This is an incredibly important issue. I think we should have a full-scale debate of the issue and in a process where we can come to the best language that the body would agree to.”

Specifically, the GOP leadership is seeking up-or-down votes on legislation authored by Sen. Wayne Allard (R-Colo.) that bans same sex marriage and an amendment written by Sen. Gordon Smith (R-Ore.) that simply defines marriage as a union between a man and a woman.

In a Monday evening exercise in gamesmanship, Frist and Reid tried to convince the other to accept their party’s terms of debate to no avail, setting in motion the process for the Wednesday procedural vote.

Earlier in the day, Frist joined supporters of the constitutional ban of same-sex marriage in a room located just steps off the Senate floor. At the rally, Matt Daniels, president of the Alliance for Marriage, acknowledged their goal of enacting an amendment banning same-sex marriage will not happen this year. A constitutional amendment needs 67 votes to receive Senate approval.

“Today marks the beginning of the debate that we wanted to see three years ago, a democratic debate, over the future of marriage in America,” Daniels said. “This debate preceded the election and it will continue after the election.”

It is unknown how many votes the Republican leadership will be able to muster for the cloture vote Wednesday, but it is likely they will fall short of the 60 needed to move forward with the debate.

Several Republicans such as Sen. Lincoln Chafee (R.I.) have indicated they would oppose the measure.

“The courts have ruled on this and I don’t see the need for a constitutional amendment,” Chafee said. “The courts have interpreted our Constitution.”