Here's a political reality check — Southern-style.

When John Kerry (search) chose John Edwards (search) to be his running mate, Democrats predicted that the presence of the North Carolina senator on the ticket would increase its appeal in the Republican South.

In the coming days, though, Senate Republicans are working to ensure that Kerry and Edwards cast votes that could alienate voters in the Bible Belt, Florida Panhandle and other Southern bastions. The legislation: a constitutional amendment to ban gay marriages.

No other social issue carves a wider divide between the North and the abortion. Not gun control. In the South, where as many as two-thirds oppose same-sex marriages, voters say they are far less willing to back a candidate that feels differently.

The Democratic ticket's Southern bounce could hit a speed bump.

Gay marriage, says Merle Black, a professor at Emory University in Atlanta, "goes to the heart of (Southern voters') cultural beliefs. They really believe marriage should be between a man and a woman."

While Kerry and Edwards oppose gay marriage, they argue that it is an issue that should be left to the states to decide. Both senators say they would vote no on the proposed constitutional amendment.

"It will give the Republicans ammunition against Edwards across the South. And they would use that in their advertising closer to the election," Black said.

The Senate vote would come just days before the Democratic National Convention (search) in Boston July 26-29 when Kerry, a four-term Massachusetts senator, and Edwards are nominated by their party. Supporters of the gay marriage amendment acknowledge it is doomed to fail, and the Kerry campaign sees the timing of the vote as pure politics.

"Americans see through phony efforts to shred the Constitution of the United States for political purposes," Kerry spokesman David Wade said Thursday. "That's not conservative, that's purely divisive."

In the 2000 election, Bush big across the South, but the Kerry campaign hopes that Edwards will help them secure North Carolina and make inroads elsewhere.

The latest Associated Press-Ipsos poll found that Kerry slightly strengthened his support in the South with the addition of Edwards.

But polling done in February and March by the Pew Research Center suggests that Southerners, more than folks in any other region, will consider the gay marriage issue in the voting booth.

According to the Pew poll, 68 percent of Southerners oppose gay marriage and nearly 40 percent said they wouldn't cast a ballot for a candidate who votes otherwise. By comparison, 48 percent of those polled in the Northeast oppose gay marriage, and just 26 percent said they wouldn't vote for someone who disagrees.

"The huge question is, can Kerry and Edwards successfully separate their position on gay marriage from their position on a constitutional amendment," said Pew Research Director Michael Dimock.

Kerry and Edwards, who have missed many Senate votes while campaigning the last year, could be absent for the gay marriage amendment, but that would not go over well with gay activists, who raised $1.8 million for the campaign in a single night.

"There is a tremendous sense of urgency that Bush be driven from office," said New York gay activist Ethan Geto, calling the gay marriage issue "the greatest political motivation ever."

But Matt Daniels, who helped draft the amendment and is president of the Alliance for Marriage said, "Any politician that stands in the way of protecting marriage, does so at their peril."

Providing a bit of cover for Kerry and Edwards is that some conservative Republicans — including former Georgia Rep. Bob Barr — oppose the amendment saying they don't want the constitution littered with directives that should be left to the states. Others say it shouldn't be used as a tool for discrimination.

And some activists argue that the issue really won't sway votes, with a good portion of the electorate having decided on their candidate or influenced by other matters.

"People vote on broader issues like the economy or the war" in Iraq, said Jeff Soref, a Democratic National Committee member and major fund-raiser in the gay community. "I think that people for whom this is an important issue made up their minds a long time ago."

Even Family Research Council president Tony Perkins, a vocal proponent of the constitutional amendment, said gay marriage should be a factor in the presidential race, but it may be overshadowed by issues such as the war, the economy and terrorism.