The answer is : the president is trying to run for a third term.
The Twenty Second Amendment sets a limit on the number of times an individual is eligible for election to the office of President of the United States.
The two-term tradition was established by George Washington ( there was no term limit previously ). President Franklin D. Roosevelt became the first president in U.S history to win a third term, which caused confusion among the electorate and prompted discussions about the change of law.
The Twenty Second Amendment was approved by Congress on March 24, 1947 and it was ratified in 1957.
Under the Amendment, any individual who has been elected president twice, can not be elected again.
There had been several attempts to repeal the 22nd Amendment but non were given serious consideration.