Despite sweeping GOP gains in Iowa government Tuesday, one Democratic senator will thwart efforts to allow Iowans a vote on gay marriage. Republicans will occupy the governor's office and will control the Iowa House next year, and there's a chance that final results could give Republicans a 25-25 deadlock in the Iowa Senate. But Senate Democrats will maintain at least equal power — which will give Majority Leader Mike Gronstal authority to prevent a vote on a marriage amendment to the state constitution. "There's no mechanism whereby senators, even a majority of senators, can override the majority leader," according to Secretary of the Senate Mike Marshall, a staffer who ensures rules are followed.