Liberal commentators often point out that this White House’s approval ratings — and, by extension, its legislative agenda — are hostages to the unemployment rate. That’s true, up to a point. But it’s also true that the Obama White House placed a bet, on the policy substance and politics alike, when it made the stimulus package the centerpiece of its response to the recession. And having lost that bet, they’ve arguably been fortunate that more of their legislative agenda hasn’t been derailed. Fair or unfair, that’s just how politics works: There was never a world where Congress was going to pass the stimulus bill and health care reform and financial regulation and cap and trade and immigration reform, all in the teeth of a persistent 9-to-10 percent unemployment rate. The procedures of the Senate have been the mechanism whereby particular pieces of liberal legislation stalled and died, but the real causes of those defeats run much deeper than the filibuster.