Gay marriage and the "bandwagon effect":

The Vermont legislature overrides a governor's veto to pass a gay-marriage bill. Same-sex marriages begin in Iowa, the state legislature and governor balk at banning it, and even state GOP leaders seem lackadaisical in opposition. The New Hampshire legislature approves a gay-marriage bill. The Maine Senate approves it. D.C. recognizes gay marriages from other states, with D.C.'s own recognition of such marriages up next. The Governor of New York pushes a gay-marriage bill, and the state assembly takes it up, having previously voted for it. The legislature in Rhode Island, the "most Catholic state" in the country as one Bishop notes, strongly considers a bill. The Connecticut legislature passes one, after a court decision, and a Republican governor signs it. The Nevada senate approves a near-civil unions bill. A GOP governor in heavily Mormon and deeply red Utah backs civil unions. Colorado approves two laws, one granting significant legal protection to gay and other unmarried couples and one extending benefits to same-sex domestic partners of state employees. And Republican strategists start questioning the party's opposition to gay marriage. No wonder: For the first time ever, a national poll shows a plurality (49%) for it, while others show significant spikes in support.

All of that has happened within the past month. And, I should add, gay marriages started today in Sweden, the seventh country to recognize them. (HT: Niclas Berggren) April was the kindest month, a blossoming Spring, for gay marriage.

Is all of this a coincidence, or is it evidence of a "bandwagon effect"? Ryan Sager thinks it's the latter:

The bandwagon effect — relatively well-established in social and political science — is when voters are influenced in their opinions or votes by which side they perceive as having majority support or being the "winning" side. While partisans tend to remain committed, more undecided voters react to two basic impulses: wanting to follow the herd and assuming that the majority of people must have information that they don't. . . .

The question, then, is whether this is happening on gay marriage.

The first question, of course, is whether there's a pronounced trend toward public support. Despite a misinformed editorial from National Review earlier this year (one which will go down in history along with the magazine's pro-segregation editorials of the 1950s), the trend is clear. . . .

As . . . major polls on gay marriage and civil unions makes clear, support for both is on the rise. Civil unions are pretty clearly above the 50% mark at this point. The new ABC News-Washington Post poll is probably a little on the high end, but gay marriage has clearly come a long way as well.

So, is gay marriage picking up steam, or is this going to be an extremely gradual process?

Well, as [Nate] Silver mentions in his post, gay marriage has gained about 8 points since 2003's Massachusetts court decision; civil unions have gained about 13 points. Now, the civil-union data doesn't go back very far. But that 8 point gain over six years for gay marriage is better than the roughly 6 point gain that gay marriage saw in the nine years since 1994. . . .

Whether or not some people want to call it media bias, the message going out to the average voter on the fence is that this is the way the wind is blowing — anyone who's not on board will be left behind.

Nothing is inevitable, and the attitudes of young people can change as they age. Iowa will be especially interesting to watch. But even aside from the dramatic developments of April, Sager is right about the trend. Call it an avalanche or a bandwagon or whatever you like, the political and legal momentum is unmistakable. It's different from that other major moral and social issue, abortion. Thirty-six years after Roe we are not seeing a bandwagon effect on that issue. Thirty-six years after Goodridge things are likely to look much different. People will continue to oppose abortion long after they've stopped opposing gay marriage, even though both are lumped together now as "family values."

One major problem with the bandwagon, however, is that it will inevitably hit the stone wall of 30 or more state constitutional amendments. Unless the Supreme Court intervenes, overcoming those amendments will require not just majorities, but super-majorities of popular opinion. Many will have to be voted on by the people at the ballot box, where so far the bandwagon has been in a rut.