a cause of action for breach on the part of the obligor lies with the assignee, who will hold the exclusive right to commence a cause of action for any failure to perform or defective performance. at this stage, because the assignee "stands in the shoes" of the assignor, the obligor can raise any defense to the contract that the obligor could have raised against the assignor. furthermore, the obligor can raise against the assignee counterclaims and setoffs that the obligor had against the assignor. for example, suppose that a makes a contract to paint b's house in exchange for $500. a then assigns the right to receive the $500 to c, to pay off a debt owed to c. however, a does such a careless job painting the house that b has to pay another painter $400 to correct a's work. if c sues b to collect the debt, b can raise his counterclaim for the expenses caused by the poor paint job, and can reduce the amount owed to c by that $400, leaving only $100 to be collected.