Not since Herbert Hoover in 1940 has a former president run to reclaim the office. Not since Theodore Roosevelt in 1912 has a former president made it to the general election. Not since Grover Cleveland in 1892 has a former president actually come back to win the White House again, the only chief executive to serve nonconsecutive terms.

What former President Donald Trump is doing is without precedent in the modern primary process. He wants all the benefits of incumbency as he runs his third straight race for the Republican nomination. His last remaining primary opponent, former U.S. Ambassador to the United Nations Nikki Haley, wants him to be judged as an incumbent.