WASHINGTON — Advocates for a bill giving Utah a fourth House seat and giving the District of Columbia a vote were ready to celebrate Thursday before Republicans tossed gun rights into the mix and forced supporters to keep the champagne on ice.

A Republican procedural during a House debate tacked anti-gun control language onto the bill and made the Democrats postpone a scheduled floor vote on the bill to an unspecified date.

Republicans attacked the bill for being unconstitutional most of Thursday afternoon. Some took issue with Utah's potential new fourth seat being an at-large district, which they claim creates two votes for the state's residents, while others have problems with a vote going to the District because it is not a state.

The bill gives Utah a new House seat ahead of when it will likely get one after the 2010 Census because a Republican member would balance out the probable Democratic member who would be elected from the District.

The bill's supporters were just waiting for the bill to pass, with House Speaker Nancy Pelosi, D-Calif., saying it was a "happy day" for the "carefully crafted bipartisan legislation" to allow District residents to finally have a vote.

But a vote on the vote never came.

Rep. Lamar Smith, R-Texas, offered a motion to send the bill back to House committees to add language that would reject the District's current ban on residents owning firearms.

"My colleagues on the other side of the aisle have suggested today that District of Columbia citizens have the 'right' to a vote in Congress," according to Smith's statement. "If that's the case, then they must also agree that the citizens of the District should have the constitutionally guaranteed right to possess firearms ... the prohibition of firearms in the District of Columbia is as ineffective and deplorable as it is unconstitutional. It is high time we rectify this wrong."

This put Democrats who were eager to pass the bill in an uncomfortable position because they would have to vote in favor of removing a gun-control ban in order to approve the voting-rights bill.

The Democrats countered by postponing the vote, giving them the option of introducing it under new floor procedure rules that could block out such an option.

"They knew we had the votes, that's what they put a lethal amendment on," said Del. Eleanor Holmes Norton, D-D.C. "I know that we're going to win."

Rep. Tom Davis, R-Va., who worked with Norton on the bill, called the move a "ploy" but made clear the bill would be back.

"This is a small setback," Davis said. "Everybody was playing their best hand here."

Davis said the "poison pill" on gun control would have killed the bill in committee.