In Minnesota, the Knights of Columbus are best known for hosting charitable free-throw contests, collecting pennies to support seminarians and conducting Tootsie Roll drives to aid people with disabilities.

Less well known is that members of the nation's largest Catholic fraternal organization are quietly positioning themselves to be a powerful and potentially decisive force in passing the marriage amendment, which would amend the state Constitution to define marriage as between one man and one woman.

The state branch of the Knights has spent months raising money, staffing phone banks and leading seminars urging people to vote for the measure. The Minnesota Knights of Columbus are following a battle-tested formula used in several other states that passed marriage amendments. The local chapters quietly provide fundraising and crucial organizational infrastructure while the national organization pumps millions of dollars into major groups masterminding the effort to block laws around the country allowing same-sex marriage.

The Knights "have been a major financial supporter of projects of the Vatican and the U.S. bishops, particularly on marriage-related issues," said political scientist Thomas Reese, a Jesuit priest and senior fellow at the Woodstock Theological Center at Georgetown University in Washington, D.C. "When any of these groups have big projects, this is the group they turn to. They have pretty deep pockets."

$3.6 million in 4 years

In the last four years, the group has given at least $3.6 million to groups leading marriage fights across the country. Now the group is trying to make its mark in Minnesota, and has directly given more than $130,000 to the fight.

The Minnesota chapters so far have given at least $31,000 to pro-amendment groups. The national headquarters has given another $100,000. But the group's 43,500 Minnesota members could prove far more valuable. In a race shaping up to be decided by a razor-thin margin, a committed bloc of thousands of energized, like-minded voters could make all the difference.

Craig Larson, state deputy of the Minnesota Knights of Columbus, said local Catholic leaders specifically asked the Knights to take a front-and-center role in the amendment fight.

"They are part of the grass-roots team, there's no doubt about that," said Jason Adkins, executive director of the Minnesota Catholic Conference, which is working to pass the measure. "We are grateful for the support of the Knights of Columbus."

The Knights were involved in the Minnesota marriage issue long before Republicans in the Legislature succeeded in getting the measure on the ballot.

In 2010, the group created DVDs that carried an anti-gay marriage message from the Twin Cities archdiocese to 400,000 Catholic households -- a move that angered many Catholics more supportive of same-sex marriage.

Several longtime Catholics who oppose the marriage amendment said they were surprised and troubled by the Knights' involvement in the marriage issue. They said they only knew the group for its charity work, locally and abroad.

Now they are crushed to learn the group is at the forefront of the anti-gay marriage effort and that some of their contributions might have gone to the cause.

"I don't think it is at all clear to the congregations," said Greg Seivert, a lifelong Catholic from Mendota Heights. When he was growing up, Seivert said, the Knights "were a charitable group that did the work of charity and mercy. This strikes me as a very different role. I would be very leery of contributing in any sort of way with their involvement in this political brouhaha."

Leaders with the Knights say their involvement in the marriage issue is completely in tune with their work around the world promoting laws that protect families, religious liberty and the sanctity of life.

"That's what we are here for, to defend our faith and to carry out the work for our bishops and priests, along with all the other charitable work that we do," Larson said.

On Nov. 6, Minnesotans will settle what has been the most expensive and divisive issue of the election season.

Minnesota law already bans same-sex marriage, but supporters say the amendment is needed after recent judicial and legislative attempts elsewhere to redefine marriage.

Marriage amendment opponents say the measure will doom the chances of gay and lesbian couples to one day marry.

Generally in their 60s and 70s, Knights often are most visible in Catholic churches or in parades, bearing swords, colorful regalia and hats with vivid plumage.

Insurance arm funds work

The bulk of the national group's significant financial firepower comes not from its 1.8 million members, but from its lucrative and highly rated life-insurance business, Knights of Columbus Insurance.