President Barack Obama's May 9 announcement in support of gay marriage has fueled interest in Minnesota's gay marriage debate.

Voters in the state will decide in November whether to amend the Minnesota Constitution to define marriage as a heterosexual union.

CNN quoted Richard Carlbom on Saturday as saying that the number of volunteers signing up for Minnesotans United for All Families, the umbrella group working to defeat the measure, more than doubled the day after Obama's historic shift from supporting civil unions to marriage for gay and lesbian couples.

Also energizing the campaign was passage of Amendment One, North Carolina's gay marriage ban.

“[Obama's decision and North Carolina's vote] was an incredible one-two punch for us in Minnesota in terms of punching up the amount of energy,” Carlbom said.

Supporters of the amendment also said the president's message has aided their cause.

“[President Obama's] comments … alerted our base to the fact that there are politicians who are trying to meddle with the definition of marriage,” Chuck Darrell, communications director for Minnesota for Marriage, told the network. “When they hear that they're motivated to get out and do something to pass the marriage amendment.”

“That will energize them to make phone calls, knock on doors, and make sure they turn out in November,” added John Helmberger, the group's chairman.