Many Republicans believed after the 2004 election that 11 ballot measures to ban gay marriage brought conservative voters to the polls and helped to increase President Bush’s vote over 2000. There’s good reason to doubt the 2004 story, notably the fact that the increase in Bush’s share of the vote rose just slightly less in the marriage-ban states than in the other states.

But now there’s new evidence that this isn’t going to be a winning issue for Republicans. The Washington Post reports:

In February, a poll by the [Des Moines Register] newspaper found that 56 percent of Iowans were opposed to legislative efforts to pass a constitutional amendment to ban same-sex marriage. That is consistent with other swing states: Voters back gay marriage by 21 points in Florida, 15 points in Ohio and nine in Virginia, new Washington Post polls found.

Read that again: “Voters back gay marriage by 21 points in Florida, 15 points in Ohio and nine in Virginia.”

The poll also found that nationally 63 percent of the tiny number of genuine swing voters support gay marriage.

No wonder Romney isn’t talking about it.

Another Post article gave more details on the swing-state polls:

In Florida, 54 percent of voters think same-sex marriage should be legal, while 33 percent say it should be illegal. In Ohio, 52 percent say it should be legal, while 37 percent say it should be illegal.…In Virginia, the nine-point gap between those who support and oppose same-sex marriage — 49 percent in favor and 40 percent opposed — represents a significant gain in support compared with a Post poll in May, when 46 thought it should be legal and 43 percent said it should be illegal.

And then there’s this, which is perhaps more important for the future than for next month’s election:

Age is an important factor: About two-thirds or more of those younger than 40 support legalizing gay marriage in each state. Among voters ages 40 to 49, the figure in Florida is 58 percent, but that dips to under half in Ohio and Virginia. Those ages 50 to 64 appear more divided, with a majority of seniors in Ohio and Virginia opposed to gay marriage.

Whatever happens in this year’s elections, in the long run Republicans are on the wrong side of this issue. And some Republicans are noticing.