How we cite our quotes: (Sentence)
Quote #1
And to answer those questions let me say this: not a cent of the $18,000 or any other money of that type ever went to me for my personal use. Every penny of it was used to pay for political expenses that I did not think should be charged to the taxpayers of the United States. (15-16)
Nixon's saying that not only isn't he rich, but he's virtuous. He wouldn't even dream of burdening the taxpayers.
Quote #2
Let me say, incidentally, that some of you may say, "Well, that is all right, Senator, that is your explanation, but have you got any proof?" And I would like to tell you this evening that just an hour ago we received an independent audit of this entire fund. (61-62)
This is Nixon's first line of defense against accusations of impropriety. Maybe he didn't think that the people would believe him, so he got independent corroboration that none of the contributions to the fund could be considered personal income. He mentions that he personally asked for this audit, so how could there be anything to hide?
Quote #3
How can we believe what you say -- after all, is there a possibility that maybe you got some sums in cash? Is there a possibility that you might have feathered your own nest?" And so now, what I am going to do— and incidentally this is unprecedented in the history of American politics—I am going at this time to give to this television and radio audience, a complete financial history, everything I have earned, everything I have spent and everything I own, and I want you to know the facts. (68-70)
This is Nixon's trump card, his ultimate testimony that he's an honest fellow who you can believe and trust. Or at least, he hoped that's what it would be, as there was a decent chance it would fall flat and just make him look like a complete idiot.