The 17-month campaign opposing the gay marriage ballot measure kicked off in earnest Monday evening at a packed fundraiser in downtown Minneapolis featuring Gov. Mark Dayton.

More than 100 people attended the event, which was hosted by Minnesotans United For All Families. The coalition of groups opposing the gay marriage amendment has been organizing for three weeks, but Monday was its first major public event.

Apart from Dayton, other boldface names in the crowd included Minneapolis mayor RT Rybak, Rep. Steve Simon and John Taft, CEO of RBC Wealth Management.

Dayton said he will ardently fight the amendment, which he was unable to veto.

"We're going to show a handful of Minnesotans that all the rest of Minnesotans are much much better than they might imagine," Dayton told the crowd.

"I will do everything I can to work with you next year to oppose this amendment," the governor said. "It violates every principle, every moral principle, every religious principle, every civic principle in my being."

He added that it was "un-Minnesotan."

Taft, who descends from the political family, said he would encourage others in the business community to oppose the measure.

"My role in this campaign ... will be to mobilize the business community and engage other CEOs just like me, who I know from talking [with them] feel exactly the same way that I do about this amendment," Taft said. "And that is it is bad for business in the state of Minnesota."

He added that "bad weather and high taxes" already make it challening to recruit people to Minnesota. "The governor's not here, but I would have pulled my punch and said the 'perception' of high taxes," Taft quipped.