Yes: 37 percent

No: 52 percent*

WASHINGTON (PPP, June):

Yes: 51 percent

No: 42 percent

The Human Rights Campaign, which on Monday announced it is putting $1 million into the four states' pro-gay-marriage campaigns, believes this will be the year things turn around for same-sex marriage at the polls. "We are poised to turn the tide," HRC's Michael Cole-Schwartz told me, though he stopped short of predicting a clean sweep: "That could mean all four states or just some of them; it's too early to tell."

But advocates are convinced their long line of shutouts will come to at least a partial end. "While we had, unfortunately, a losing streak, those losses date back to 2004 and 2006," Cole-Schwartz said. "In 2012, we're working in an entirely different environment."

Public opinion has shifted rapidly in favor of gay marriage in recent years; a recent CNN poll found 54 percent of Americans supporting legal recognition of "marriages between gay and lesbian couples," part of a long-term public opinion trend in that direction. Since President Obama came out in favor of gay marriage in May, there's evidence the position has gained even more support among Democrats, particularly African-Americans, and the Democratic Party recently announced there will be a pro-gay marriage plank in the platform approved at the convention in Charlotte next month.

Also working in the measures' favor is the fact that all four are on the ballot in liberal-leaning states unlikely to be contested in the presidential election. The measures differ slightly: In Minnesota, gay-marriage advocates are hoping to beat back another state constitutional amendment banning gay marriage; in Maryland and Washington, anti-gay marriage groups are hoping to overturn marriage liberalization laws passed by state legislatures; and in Maine, a referendum to legalize gay marriage would, if passed, supersede a 2009 voter referendum banning it.

Supporters of gay marriage also believe they have gotten more sophisticated with their approach to messaging. New ads in Washington, such as the one above, emphasize the love and commitment of gay couples. Earlier efforts tended to highlight the rights and benefits that come with marriage, like hospital visitation, but research has shown that that's a less convincing approach. "It doesn't capture the emotional connections people have with marriage," Cole-Schwartz said.

It would, however, be premature to declare victory for gay marriage at the ballot box. Efforts to ban same-sex marriage have frequently lagged in public polling only to prevail on election day, noted Brian Brown, president of the National Organization for Marriage, which backs such efforts. Brown said his group has so far given about $600,000 to the state anti-gay marriage efforts and plans to spend more than $1 million. (The Human Rights Campaign's new $1 million expenditure brings the group's spending on this year's initiatives to nearly $5 million.)