Immigration reform is the most important policy question facing Republican lawmakers as they begin their August break. But it’s not the hottest topic in the GOP political world, not the one that dominates talk radio and the daily debate. That is the move to defund Obamacare.

With immigration, Republicans have the power to determine the outcome of reform legislation that has passed the Senate but still must make its way along a difficult path in the GOP-controlled House. Obamacare, on the other hand, is already law, and Republicans, without control of the Senate or White House, can’t do much to stop the flow of health care subsidies set to begin January 1, 2014.