In all the decisions I have made in my public life, I have always tried to do what was best for the Nation. Throughout the long and difficult period of Watergate, I have felt it was my duty to persevere, to make every possible effort to complete the term of office to which you elected me.

In the past few days, however, it has become evident to me that I no longer have a strong enough political base in the Congress to justify continuing that effort. As long as there was such a base, I felt strongly that it was necessary to see the constitutional process through to its conclusion, that to do otherwise would be unfaithful to the spirit of that deliberately difficult process and a dangerously destabilizing precedent for the future.

But with the disappearance of that base, I now believe that the constitutional purpose has been served, and there is no longer a need for the process to be prolonged.

—President Richard Nixon
August 8, 1974

What, according to Nixon, has caused him to change his mind about “persevering”?
a loss of support in Congress

the realization that he is guilty of wrongdoing
a lack of support by the general public
disillusionment with the constitutional process