DALE CARPENTER: Is there a rising tide of GOP opposition to a Minnesota state constitutional amendment that would ban gay marriage?  Republicans won last fall “on promises to balance the budget, limit taxes and spending, and make the state more business-friendly. Social issues were almost totally absent from the campaign. Nevertheless, a constitutional amendment excluding gay couples and their families from marriage has been making its way quickly through the Minnesota legislature. If approved, it would go on the ballot in November 2012 in a popular referendum, where it would have to get a majority of all votes cast in a high turnout year. It had seemed the amendment would sail through the state legislature. But now it faces rising Republican opposition.”