(Reuters) - Victim advocates and former prosecutors used the anniversary of the 1995 Oklahoma City bombing on Tuesday to lobby the U.S. Senate on behalf of U.S. Supreme Court nominee Merrick Garland, who oversaw the prosecution of bomber Timothy McVeigh. The group, which also includes law enforcement officials, said in a letter to Senate leaders that Garland, a federal appeals court judge picked by President Barack Obama for the Supreme Court, is a man of “integrity and brilliance” who proved his mettle in obtaining the conviction of McVeigh. “Twenty years ago, the nation could not find a better lawyer to manage the investigation and prosecution of what was then the worst crime ever committed on American soil. Today, our nation could not find a better judge, nor a more honorable man, to join its highest court,” the group of 15 connected to Garland through the case said in the letter. It was the latest effort by Garland supporters to put pressure on the Republican-led Senate to act on his nomination to fill a vacancy created by the Feb. 13 death of conservative Justice Antonin Scalia. Republicans who control the Senate are refusing to advance the nomination, prompting Democrats to accuse them of obstructionism and of ignoring their constitutional obligations. Republicans insist the next president, to be elected on Nov. 8 and take office Jan. 20, fill the vacancy, hoping a Republican will win the White House and choose a conservative rather than the centrist Garland. McVeigh used a fuel and fertilizer bomb to turn Oklahoma City’s Alfred P. Murrah Federal Building into a tomb of rubble on April 19, 1995, killing 168 people.  More than 680 people were injured in the attack. McVeigh was later executed.  In the letter that included former Deputy Attorney General Jamie Gorelick, Garland’s boss at the time of the McVeigh trial, the group credited him with running an intricate and complex operation to secure a conviction that would stand up to any sort of appeal. “The pressure to get it right was unyielding – and Judge Garland’s support was critical. He was not just a supervisor; he was a mentor, a counselor, and a friend,” the letter said. In Oklahoma City on Tuesday, the remembrance ceremony was held in a church near the blast site and marked with prayers and 168 seconds of silence for the victims.  