Answer:
Retirement.
Step-by-step explanation:
Antonyms are words that have the opposite meanings of one another. In this way, we can know that the words "acceptance" is the opposite of "resignation". This can provide us the best clue for what the term "resignation" may mean or imply.
To resign means to give up, to let go, to be free of something. And in the use of the word "resignation" in the given passage, we can infer and conclude that it means the retirement of President Nixon after the Watergate scandal. So, the word 'resignation" in the given passage means President Nixon resigned, voluntarily gave up his office, retired.