Forget the "gender gap." The bigger factor this year may be the "marriage gap."

Townhall's Jeff Jacoby writes that married voters lean toward Republican candidates, while singles favor Democrats. That could be one big reason Obama leads Romney in the polls right now. Obama grabbed 70-percent of the single woman vote in 2008. This year, unmarried women support Obama by a 2-1 margin over Romney.

The political stakes are clear. Single women, one of the fastest-growing population cohorts, already account for one-fourth of all eligible voters. They are the "most reliably Democratic voting group outside African Americans," writes Washington analyst Jessica Gavora, and coaxing them to the polls is an urgent priority for Obama's strategists. That explains the Democrats' whipped-up accusations of a GOP "war on women." And it explains the Obama campaign's "Life of Julia," an internet slideshow that depicts a woman reaping the benefits of government programs at each stage of life. With help from "President Obama's policies," Julia is able to get an education, go to work, access health care, raise a child, launch a business, and retire in comfort. Everything, it seems, but get married.

What explains the marriage gap? Why, as Gallup editor-in-chief Frank Newport notes, is marriage a predictor of more conservative views, while being unmarried is a predictor of more liberal views?

One reason may be that people who are conservative to begin with are more likely to get married. This seems to be the case in religious circles. Higher marriage rates correlate with more frequent church attendance; religious commitment in turn is a strong predictor of party identification.