The group trying to legalize same-sex marriage in Minnesota has crafted a fundraising appeal to capitalize on a Republican legislator's announcement that he plans to co-sponsor the bill.

"And in breaking news today, Republican State Senator Branden Petersen is preparing to co-sponsor legislation to ensure that same-sex couples have the freedom to marry in Minnesota!" Minnesotans United wrote in a fundraising plea Wednesday.

The Star Tribune first reported that Petersen, R-Andover, is prepared to sign onto the proposal that would legalize same-sex marriage. Petersen, a first-term Senator who previously served in the House, is the first Republican to announce support for the measure.

"It couldn't be more clear: The momentum is with us," Minnesotans United wrote. "Minnesotans believe in freedom, fairness and the importance of marriage -- for everyone. Together this year, we can prove that Minnesota is the kind of state that values and protects all families."

Minnesota for Marriage is holding a rally early next month to rally supporters and pressure legislators not to legalize same-sex marriage.

Same-sex marriage supporters expect to unveil their bill early next week.