Senate Republicans are holding up all the chamber's business to push their top priority of giving the wealthy an unpaid-for tax cut. Meanwhile, the Build America Bonds program, which I have defended before, is set to expire at the end of the year. The bonds are unlike those normally issued by states and cities because they aren't tax-exempt, but rather have a tax credit, lowering costs and opening up the bond market to nonprofits; they also eliminate the incentives that have made many typical tax-exempt muni bonds into little more than glorified tax shelters.