WASHINGTON — President Trump asked Sen. Orrin Hatch, R-Utah, to stay away from his inauguration on Friday for an important reason.

As the senior Republican in the Senate, Hatch expected to join the president's escort to the dais on the steps of Capitol Hill and to sit in a prominent seat. Instead, Trump selected him as the designated survivor who would ensure the continuity of government in case catastrophe struck the swearing-in ceremony, where all the nation's leaders were gathered in one place.

Hatch traveled to a distant, undisclosed and secure location to fulfill that duty.

"At the request of President Donald Trump, I am honored to fulfill the role of designated presidential successor during the inauguration," Hatch said in a news release. As much as I would have liked to participate in the ceremony and festivities, I am honored to perform this important constitutional duty, which ensures the continuity of government."

Trump's choice made Hatch, who is president pro tem of the Senate, unique in inaugural history. He is the highest-ranking person to serve as a designated survivor on inauguration day.

Hatch is third in line to the presidency, after the vice president and speaker of the House. If those three resigned or died or were removed from office, Hatch would become acting president.

Hatch did serve as the designated successor to during President Obama's 2016 State of the Union address. He was the second president pro tem to serve in that role. Sen. Ted Stevens, R-Alaska, served as the designated survivor for George W. Bush's 2005 and 2006 State of the Union speeches.

In the past, a designated survivor, a role born in the Cold War under the specter of nuclear war, has been provided with presidential-level security and transportation, according to a 2007 CBS News story. A military aide is also alongside with the "football," the briefcase with nuclear missile launch codes.