Voters in New Mexico's largest city will decide Tuesday whether to ban late-term abortions.

The municipal referendum is believed to be the first of its kind in the country and is being watched as a possible new front for activism in the abortion wars that have typically been waged at the federal and state levels.

The outcome is anyone's guess following an emotional and graphic campaign that brought in national groups and hundreds of thousands of dollars on advertising.

More early voters turned out than in last month's mayoral election, but there has been no polling and the city clerk has not released voters' party affiliation.

If the referendum passes, a legal challenge is expected. Attorney General Gary King, a Democrat, has said he believes the law is unconstitutional.