Here's a guy who was clearly conflicted about Tonkin Gulf Resolution. In a single statement during Congress' debate over the document, he gives the thumbs up but also is clearly unsure.

"I do not know what the limits are […] I think it would indicate that [the President] would take reasonable means first to prevent any further aggression, or repel further aggression against our own forces." (Source)

First, note that this quote shows how Fulbright accepts the fact that the power is in the President's hands in this military engagement. Repelling further aggression is good, right?

Yeah, but note his hesitancy. He's talking only of preventing aggression, probably referencing the alleged attacks on U.S. ships. Did he know the result would be a full blown war with hundreds of thousands of ground forces? Fulbright goes on to say:

I do not know how to answer the Senator's question and give him absolute assurance that large numbers of troops would not be put ashore. I would deplore it…

Wait a minute, he would deplore it? As in, he would be strongly against it? Guess what Shmoopers, "large numbers of troops ashore" is exactly what ends up happening.

We wonder if Fulbright would have reconsidered his vote if he had known.