The lead group backing the marriage amendment on Wednesday accused the other campaign of stalking supporters on social media.

"For those who support the Minnesota marriage protection amendment, this is simple harassment," said Autumn Leva, spokeswoman for Minnesota for Marriage. "This latest move …. also demonstrates the type of behavior Minnesotans will see more of if marriage is ever redefined."

The group is reacting to a recent Facebook post by a leader of Minnesotans United for All Families urging supporters to use a special program to identify and then contact their Facebook friends who might be voting in favor of the measure.

In a Facebook post, Minnesotans United campaign manager Richard Carlbom asked: "Which of your Facebook friends are planning to vote YES on the hurtful marriage amendment? … This new tool is linked up to a list of our targeted voters. If they are on the list, they are the Minnesotans likely to determine this Election in just 52 days. Check out which of your friends plan to vote YES and then go have a conversation with them! Please, help me spread the word!"

Kate Brickman, a spokesman for Minnesotans United, said the other side is erroneously characterizing what the technology does.

"The fact that they are trying to say this is an outrageous lie," she said. "It's ridiculous."

Brickman said the program is no different than any phone bank, which both campaigns use to identify supporters and opponents.

The program does not give access to names outside of the user's list of Facebook friends, Brickman said. It merely identifies Facebook friends who are on the group's list of people who might be voting for the measure. By identifying Facebook friends voting 'yes,' it gives a user who opposes the measure the chance to have a conversation with them.

To try it yourself, go to: know.mnunited.org.

The marriage amendment campaign is shaping up to be one of the most expensive, nasty and unpredictable of the election season.

Supporters of the measure want to change the Minnesota constitution to only recognize marriage as a union between a man and a woman. Minnesota law already bans same-sex marriage, but supporters argue that the change is needed to prevent future judges or legislators from changing the law.

Marriage amendment opponents argue that the measure would limit the freedom of gay and lesbian couples to one day marry. They say that gay couples in loving and committed relationships deserve the same rights as straight couples.

Marriage amendment supporters have fallen behind in fundraising, but most polls show the measure passing or close to it.

Leva said voters need to approve the measure because in other states and countries that legalized same-sex marriage, defenders of traditional marriage "are not only stalked by a social media 'election profiling' tool, but also treated as bigots."