The Winner on Tuesday

If, in the runup to the midterm elections, the opinion polls are correct — a big if, to be sure — the winner in Tuesday’s voting will likely be the idea of divided government. In other words, a split between the parties controlling the levers of the federal leviathan. To appraise the midterm outcome through this constitutional lens means tempering talk of triumphalism on the part of the Democrats and, for that matter, the Republicans.