Let’s take only the Obama presidency. Had the filibuster not applied, the United States would have a market-based system to control carbon emissions, which would limit the damage from global warming, vitalize the clean technology sector, and challenge other large polluters like China and India to do the same. The new health care law would have a public option. Children of undocumented immigrants who served two years in the military or went to college could become US citizens. Women paid less than their male colleagues because of their gender would have broader legal recourse against their employers. Billionaires would not be able to manipulate the political system from behind a veil of anonymity…

This no-filibuster fantasy world might strike conservative readers as less than ideal. But Republicans may win control of the Senate and White House this fall. Then they’ll be the frustrated ones.

An intransigent Democratic minority would block much of what Republicans are most eager to accomplish. For instance, they almost certainly couldn’t repeal the dreaded “Obamacare” (although the Supreme Court may strike it down next month). Nor would Romney’s vow to deregulate Wall Street by undoing the Dodd-Frank financial reforms stand a chance, anymore than the various plans to cut entitlements like Medicare, Medicaid, and food stamps. Extend the Bush tax cuts for the rich?