As Republican Senators travel throughout their respective states this week, party leaders are urging them to promote a constitutional amendment that bans gay marriage — a move that breathes new life into the controversial topic less than six months before the November elections.

While Senate Republican Conference Chairman Rick Santorum (Pa.) acknowledged that supporters of the ban don’t have the 67 votes needed to send the measure to the states for ratification, he vowed to force a vote on the issue before the election, to compel Senators to take a position on the issue.

“I intend to work very hard to get a vote,” Santorum said. “I have made it clear that is my desire and I believe the Senate should go on the record.”

Massachusetts’ decision to sanction gay marriages last week prompted lawmakers and socially conservative groups such as the Traditional Values Coalition and Christian Coalition of America to renew calls for a constitutional amendment to ban same-sex unions.

Republican Senators were issued talking points on the subject twice last week, first as part of the GOP’s weekly message plan Tuesday and later in a Memorial Day recess packet that also emphasized other issues such as the economy and the Iraq war.

“This is a national crisis that requires a national response — a federal constitutional amendment,” according to one of the talking points contained in both packets.

In addition to nine bullet points on same-sex marriage, the GOP memo also includes the “Top Five Reasons to Defend Marriage.”

Of these, No. 3 is: “Redefining marriage sends a terrible message to the next generation: alternative family forms are just as good as traditional families, and children don’t need mothers and fathers.”

The Senate and House have held hearings on the subject, and while GOP leaders mostly support a ban on gay marriage, the timing of a vote on a constitutional amendment remains unclear in both chambers.

Senate Majority Leader Bill Frist (R-Tenn.) said that a “constitutional amendment … is consistent with the values of the United States of America,” but he would not commit to a specific date for a vote. A spokesman for House Majority Leader Tom DeLay (R-Texas) also would not offer a fixed date when the legislation would come up for a House vote.

“We are not at a point yet where a consensus is clear,” said Jonathan Grella, a DeLay spokesman. “It is hard to speculate when the right time would be.”

Still, groups that oppose same-sex marriage are urging that a vote be held no later than early October so that they can build a political campaign around the issue.

“We want all 535 Members to be on the record,” said Jim Backlin, the vice president of legislative affairs at the Christian Coalition.

For Sen. Wayne Allard (R-Colo.) — the chief sponsor of the Senate legislation that would institute the ban — Congress can’t act soon enough. “We ought to get it out to the states,” he said.

Santorum — one of 14 Senators who have co-sponsored Allard’s legislation — said that it is “fine” for a gay couple to live together, but he opposes the effort by gays and lesbians to “change the definition of marriage to meet their unique circumstance.”

The sanctioning of gay marriages in Massachusetts, combined with other activity taking place elsewhere, proves that this is a national crisis, Santorum said.

“When you change something that is foundational to the country — as the family structure [is] — I can’t think of anything that is more of a crisis than the deterioration of the American family,” he said. “I think this is going to be a very significant contributing factor to that.”

But Santorum is not expected to convince all of his GOP colleagues to support a constitutional amendment banning gay marriage.

“Well, you just have to come to grips with homosexuality,” said Sen. Lincoln Chafee (R-R.I.). “And once you have done that — [once you] cross that threshold of saying, ‘This exists’ — then better human nature should come out. With all the talk of freedom, freedom, freedom in every sentence by the administration, here is the chance to do something to show they mean it,” Chafee added.

President Bush released a statement last week urging “Congress to pass, and to send to the states for ratification, an amendment to our Constitution defining and protecting marriage as a union of a man and a woman as husband and wife.”

But Republicans are not alone in having to reconcile intraparty differences on gay marriage.

Many Democratic Senators, such as presumptive Democratic presidential nominee John Kerry (Mass.) and Minority Leader Tom Daschle (S.D.), oppose gay marriage. While Sen. Zell Miller (Ga.) is the only Democrat to sign onto Allard’s bill so far, the Democrats are on the defensive during this campaign season. The party needs to defend five open seats in the South, plus Daschle’s seat — all races taking place in states that trend conservative on social issues.

In the House, several Democrats have signed on as co-sponsors to a bill sponsored by Rep. Marilyn Musgrave (R-Colo.) to approve a constitutional amendment banning gay marriage.

Santorum said a vote on a constitutional ban would force Democrats to publicly state their position on the issue. Sen. Dick Durbin (D-Ill.) — who said he opposed same-sex marriage and a constitutional amendment to ban it — accused the Republicans of trying to divert attention from the economy and the war in Iraq by trying to focus attention on a subject that had little hope of passing this year.

“This is ‘Operation Change the Subject,’” Durbin said. “So they are going to try to make the issue of same-sex marriage the defining issue of the campaign. I don’t think it is going to work.”

Still, a top official for the Human Rights Campaign — a leading advocacy group for gay, lesbian, bisexual and transgender interests — said that the organization will do everything possible to prevent the legislation from passing in either chamber.

“We remain vigilant in our advocacy against writing discrimination into the Constitution,” said Winnie Stachelberg, the group’s political director. “We have confidence that the American people want to spend their Memorial Day recess talking about a whole host of other issues, not discriminating against hard working American families.”