Sen. Wayne Allard, a Colorado Republican, said he expects GOP leaders to call for a vote before the 2006 elections and added, "I think it would be foolhardy to back off when we've got a good head of steam coming out of the election." The amendment fell far short of passage a year ago.
Vote counters on both sides agree that Senate backers of the amendment picked up support in the 2004 elections.
Most Democrats signaled their opposition to the measure on the vote last year, and Bush and others have said it's unlikely there will be much of a change in senatorial sentiment unless there is a court ruling requiring one state to recognize same-sex marriages performed in another.
But Allard said he thought some opponents might reconsider more quickly in the wake of fall's elections. "I know the Democrats are re-evaluating their position on a number of social issues, and I'll bet this is one of those issues," he said.
There was no immediate evidence of a switch among opponents.
"The Democratic Party is still opposed to this amendment," said party chairman Terry McAuliffe. "It is wrong to write discrimination into the U.S. Constitution, and it is shameful for Washington Republicans to attack gay and lesbian families for purely political reasons."
Bush pushed hard for a vote in both houses of Congress on the amendment during last year's election campaign. This year, he said he will not lobby the Senate to pass the amendment, adding there are not enough supporters to approve the measure.
When social conservatives complained, White House counselor Dan Bartlett said Bush was talking about the "legislative reality" and will continue to push for the ban.