Supporters of a gay marriage ban in Minnesota believe that forty percent of Democrats will vote for the amendment.

Voters in November will decide whether to place the state's law which bans gay nuptials in the Minnesota Constitution.

Chuck Darrell, spokesman for Minnesota for Marriage, the group campaigning for passage of the amendment, told the Bemidji Pioneer that he expects nearly half of Democratic-Farmer-Laborites (DFL) to vote for the amendment.

“We are counting on 40 percent of the DFL vote here in Minnesota to vote for the marriage amendment, and similar numbers within the minority communities,” he said.

Darrell noted that 36 percent of Democrats in 2008 favored a similar constitutional amendment in California, Proposition 8. He added that DFL efforts to increase the turnout for President Barack Obama could also help drive up the number of voters who favor the amendment.

“Support for the marriage amendment crosses every kind of boundary you can imagine,” Darrell said.

At the same time, some Republicans, in particular libertarian-minded voters, are increasingly speaking out against the measure.

(Related: Minnesota Democrats oppose gay marriage ban at state convention.)