ST. PAUL, Min. (MNN) -  The number of constitutional amendments the Republican-controlled Minnesota Legislature could put on the ballot in 2012 is building.  So far this week, three constitutional amendments have been proposed -- one that would require a three-fifths majority of both the House and Senate to pass any state tax increases, and two others which have hearings today.  One would prohibit same-sex marriage in Minnesota, the other would require voters to present photo ID before they receive their ballot.  Carleton College political science Professor Steven Schier says the more constitutional amendments Republicans put on the ballot, the smaller the probability that any of them will pass.  Another consideration -- if someone doesn't vote on a constitutional amendment, it effectively counts as a "no" vote.