"Many of those who followed in Sander's wake adopted his understanding of Judaism, but not his view of Paul. In other words, they agreed with Sanders's assessment of Paul's context (i.e., the Judaism to which Paul responded) but not Paul's content (i.e., Paul's response to Judaism). Sanders argued that Paul attacked Jewish legalism, but only because he misunderstood the Judaism of his day. New Perspective adherents assert that Paul understood Second Temple Judaism, and therefore he did not attack Jewish legalism, but Jewish exclusivism.
"Responses to Sanders and the New Perspective have followed four different tracks. First, some scholars responded exegetically by contesting the New Perspective reading of Paul's epistles. Second, scholars have reevaluated the Judaism of Paul's day and begun to question Sanders's one-sided reading of Second Temple Judaism. Some scholars then combined both of these elements in contesting the New Perspective. Fourth, some studies now call the New Perspective's reading of Luther into question."
You can read the introduction from which this portion comes here.