Senate Republicans prepared two versions of a constitutional amendment on marriage Monday, unable to agree among themselves on how best to get a vote on a measure that President Bush (search) made an election-year priority for Congress.

The likely outcome is that neither proposal will get a direct vote after Democrats just last week had agreed to allow one.

Senate Majority Leader Bill Frist (search), R-Tenn., said there was "great interest" among Republicans for a simpler approach that would add only one line to the U.S. Constitution: "Marriage in the United States shall consist only of the union of a man and a woman."

Democrats rejected Frist's request to hold votes on both it and the original version that included another sentence: "Neither this Constitution, nor the constitution of any state, shall be construed to require that marriage or the legal incidence thereof be conferred upon any union other than the union of a man and a woman."

Proponents of the amendment said they included the second sentence to clarify that state legislatures — but not courts — could still establish laws recognizing civil unions and domestic partnerships between two people of the same sex.

"There's been a considerable amount of debate and a lot of scholarly thought and a lot of constitutional experts that have been approached as far as what would be the best language," said Sen. Wayne Allard (search), R-Colo., who authored the original version.

Cheryl Jacques, president of the Human Rights Campaign (search), the nation's largest gay political organization, said the last-minute effort to get votes on two different versions reflected a lack of care in drafting the amendment.

"I think it is outrageous and frankly surreal that at the 11th hour in this debate, they are literally rewriting the Constitution on the back of a napkin," she said.

Democrats said opening the proposed amendment to changes could open the Constitution itself to other amendments ranging from campaign finance to flag burning.

"We're treating it like just another little old amendment," Senate Minority Leader Tom Daschle (search), D-S.D., said of the GOP demands for separate votes on each version. "This is an amendment that will be added to a document that is precious, that we treasure, that we ought to have respect for."

The only vote likely to occur now is a procedural one scheduled for Wednesday aimed at forcing the Senate to act on the amendment. Republicans, who had already conceded they lacked the two-thirds majority — or 67 votes — needed to advance a constitutional amendment, would have to get 60 votes to go on to a vote on the issue itself.

"There are really predominantly two different tracks that people would like to take here," said Sen. Rick Santorum, R-Pa. "All we're suggesting is that at least those two ideas be given the opportunity to be voted on."