In the October 10 debate between Elizabeth Warren and Scott Brown, Brown admitted that he had signed the Grover Norquist pledge to never raise taxes, ever, for anything.   And yet Brown has been asking voters to see him as a “bipartisan” Senator who will “work across the aisle.”  Given that President Obama as well as many Democrats in the U.S. Senate have been calling for more revenue, from slightly higher taxes on the rich, how can Brown possibly negotiate with them in a bipartisan way?  He has taken a most consequential option off the table.  He has made it nonnegotiable.