Let’s, however, consider what would flow from various rulings. I will focus on the clearer Defense of Marriage Act case, understanding that the California Prop. 8 case may be decided on narrower grounds that are not especially relevant to other cases.
Suppose the court decides DOMA is unconstitutional on 14th Amendment grounds, that marriage is a “fundamental right” (it has so ruled many times) and that neither the states nor the feds can bar same sex marriage. Not unlike in abortion cases, the losing side will be aggrieved, claim judicial tyranny and vow to overturn the ruling. But for all intents and purposes, the issue will be over (aside from futile efforts to pass a constitutional amendment); social conservatives will have been roundly punished for trying to federalize marriage in the first place.
If, however, the court strikes down DOMA on 10th Amendment grounds, a befitting twist on originalism and an ode to federalism (usually the carrying cards for conservative jurists and scholars), then the issue returns to the statehouses where legislative votes, referendums and state constitutional amendments will control the outcome, including potential protections for religious institutions. (In Maryland, strong protection for clergy in exercising religious liberty — i.e. the right not to be compelled to perform gay marriages — helped the gay-marriage measure pass.) Federal politicians can certainly express their personal views, but gay marriage essential ceases to be a national issue unless social conservatives imagine they are going to round up enough states to pass a constitutional amendment enabling the feds to ban gay marriage (or even worse, try to impose a gay-marriage ban in the Constitution itself).
In the 14th Amendment scenario, the political process is short-circuited; in the second, the states become lively venues for debate and legislation. If the polls are correct, in many, but not all, states, public opinion will tip the balance in favor of gay marriage.
And what if DOMA is upheld? Gay-marriage advocates will rush to seek its repeal; it may well become a significant political issue in 2014 and 2016. An alliance in favor of DOMA repeal is likely among pro-federalist conservatives (e.g. Sen. Rand Paul), libertarian-leaning conservatives and social liberals. The ultimate “wedge issue” is elevated to the national level, dividing conservatives on whether marriage should be federalized.
From a political point of view, the last scenario is, I would suggest, the worst of all possible worlds. Not only does it foment fighting within the Republican Party, but the GOP would once again be tarred as the party of exclusion, intolerance and hypocrisy (they are arguing that the feds can tell us how to marry but not what insurance to buy?). Rather than entitlement reform, the debt, taxes and education reform, a good deal of time would be spent in GOP primaries, conferences and rallies on marriage. You can bet a great many hurtful and bizarre statements would be made by anti-gay-marriage advocates (think Rick Santorum a thousand times over), and the special-interest groups on the right and left would have a field day.
Had social conservatives (and at the time, at least on the marriage issue, this included a great number of Democrats, including President Bill Clinton, who signed DOMA into law) left marriage with the states, they would not be facing obliteration of same-sex marriage bans nor would they be faced with a national political firefight that, over time, they will eventual lose, considering the movement in public opinion.
Regardless of how the court rules, democracy does matter. Public opinion over time prevails. Whether that is by judicial fiat or legislative wrangling remains to be seen. But as the country shifts from virulent opposition to gay marriage to acceptance, the laws will follow. Those who try to hold back the tide eventually get swept away.