President Trump has once again floated the idea of testing the Constitution's presidential term limits by seeking a third term, as his administration continues to challenge constitutional provisions and push an expansive view of executive power.

After telling NBC News that he's "not joking" about the possibility and that there are "methods" that would allow him to serve a third time, Trump declined to confirm to reporters aboard Air Force One on Sunday that he's planning to leave the White House after his second term ends on Jan. 20, 2029.

The 22nd Amendment prohibits a person from being elected U.S. president more than twice. The states ratified the restriction in 1951 in the wake of former President Franklin Roosevelt's controversial third and fourth terms during World War II, which bucked a two-term norm set by George Washington.