Senate Republicans attacked the attorney general Thursday for failing to disclose during his confirmation process last year that he had signed a 2004 legal brief in an important terrorism case. The GOP lawmakers signaled that the mistake will be one focus of their aggressive questioning of Eric H. Holder Jr. at an oversight hearing March 23 that is expected to highlight his handling of detainee policy and national security threats. In recent weeks, critics in Congress have seized on missteps to raise questions about the Justice Department's approach to counterterrorism. Among their biggest targets is the possible White House reversal...