Five years ago, Judge Merrick B. Garland became a high-profile casualty of Washington’s political dysfunction. President Barack Obama selected him to fill the Supreme Court vacancy created by the death of Justice Antonin Scalia, but Senate Republicans blocked his nomination. In the process, Mr. Garland became known for the job he didn’t get. Now, after being nominated by the Biden administration to become the next attorney general, Mr. Garland is finding professional qualifications under scrutiny once again. In light of the attack on the Capitol, we explore how his career leading investigations into domestic terrorism prepared him for his Senate confirmation hearing.