Conservatives are grumbling that many of the featured speakers at the Republican National Convention this week hail from the liberal wing of the party – meaning that they haven’t toed the pro-life, anti-abortion line.

But abortion is rapidly taking a backseat to gay marriage as the hot issue of the day. And while there is plenty of debate among Republicans about how best to respond to the Massachusetts Supreme Court’s decision extending marital rights to homosexuals, there is almost universal agreement that gay marriage is a bad idea that shouldn’t be foisted on the rest of the country without some form of consent.

Polls show that at least 60% of Americans oppose gay marriage, and even that figure may be understated. In the privacy of the voting booth, Missourians voted by 71-29% to limit marriage to a man and a woman. The issue is likely to be on the ballot in at least eight other states, including such battleground states as Michigan, Oregon, and Ohio, where even conservative activists have been stunned at how easy it was to round up the necessary signatures.

To be sure, gay marriage still ranks well down on the list of major concerns among most Americans, according to a recent Gallup Poll. It’s also not clear that the Republican Party’s embrace of a constitutional amendment at the federal level will sell very well. No less a personage than Vice President Cheney, who has a lesbian daughter, says he thinks the issue should be left to the states – which also happens to be Democratic contender John Kerry’s official position.

But so long as the spotlight is on the left’s support for gay marriage, as opposed to how best to oppose it, it’s likely to be a net winner for the GOP. If the race is as close as predicted, it could even be decisive. Politically, this means there is merit to the Cheney position, because it will force the left to defend what a clear majority of Americans consider the indefensible – over and over again, state by state. Only by winning the argument at this level could the GOP have any hope of winning a constitutional amendment down the road in any case, if indeed it’s still necessary.

Leaving the matter to the states has another virtue from the Republican perspective. It keeps the focus on the role of the judiciary. The continuing intrusion of activist judges into bedrock social understandings plays directly to a Bush strength: his argument that he should be allowed to appoint judges who will say what the law is, not what it ought to be. Radical decisions about gay marriage might even cause people to wonder more deeply about the legal underpinnings of Roe v. Wade, the Supreme Court’s foundational abortion ruling.

Democrats understand the danger of the gay marriage issue. Last week in Michigan, the two Democrats on the four-person state Board of Canvassers, which must certify referendums, blocked the referendum on gay marriage by claiming that it was “patently unlawful.”

But the real agenda was clear: Democrats fear that such a proposal might drive up Republican turnout in the fall. This blatantly political agenda was made even clearer by their refusal to certify Ralph Nader’s right to appear on the ballot.

Such high-handed decision isn’t likely to pass the laugh test on appeal, most observers say. The role of the Board of Canvassers is simply to certify that a measure has fairly earned the necessary support to go on the ballot. But even if a court goes along with this stonewalling, it’s only likely to further enrage the 480,000 people who signed petitions favoring the referendum – as well as a lot of other folks.

Message to the Republican National Convention: Let well enough alone. Keep the spotlight on the radical nature of what the left is demanding, not on schemes to amend the Constitution that Democrats will portray as equally risky.

The left, citing the 50% divorce rate among new heterosexual marriages, ask why straights should be so worried about gay marriage. They have a fair point. But the reaction of most Americans is likely to be that this calls for shoring up traditional marriage, not – as the late Daniel Patrick Moynihan might have put it – defining marriage down.

This is another reason for resisting the urge to put too much emphasis on silver bullets like a constitutional amendment. Opposition to gay marriage – as well as the notion of civil unions – should rest on concerns for marriage generally, not on opposition to gays. Polls also make clear that Americans have little appreciation for gay-baiting politicians. But that still leaves plenty of room for principled opposition to the radicalism of the left on gay marriage.

And if the philosophical battle against gay marriage can be won at the state level, it might not be necessary to weight the Constitution down with statements of social goals – a game that utopians of the left might be only too happy to play.