I watched Taxi Driver for the first time last night and have been searching for an intriguing analysis since. This is the one I agree with most. A few observations that have been bouncing around in my head:

1)It is highly possible that Travis was never in fact in Vietnam. He skirts away from the topic when it is mentioned at the beginning of the movie, and he never speaks to it in detail. In addition, he seems to have limited knowledge of fire arms until he starts practicing with them. It is possible that he created the fictitious back story so that others would view him as he longed to be viewed: a hero. Notice he only brings up his military past in front of bullish men who he thinks would be impressed by it. This concept would be along the same lines as hanging a witty office poster in his apartment even though he has never worked in an office. The army jacket and the office poster are symbols of his need to be viewed as something he isn't.

2)Many people speak to his loneliness as a key motivator in the movie. I didn't think this was the case. It wasn't that his loneliness drove him to insanity, it was that loneliness was a side effect of a psychological defect which he had from the beginning of the movie. He prefers being alone because he views the rest of humanity as cold and filthy. I place a large amount of importance on his letter back to his family in which he lies completely about his life, and distances himself further from them with statements like "I hope that no one has died." Has it really been that long since the last time he saw his family?

3)People seem to think the botched date w/ Betsy is what threw him over the edge. I don't agree with this point. The moment he actually changed was when Iris entered his cab. That's why he separated the $20 bill from the rest of his money, because he always planned on returning it. That was before the botched date. He always viewed himself as a hero, but he could never follow through on his own perception of himself. He was always a silent observer of wrongness without taking action. He separated the world in his taxi from the world outside of it. That changed when a victim of the world outside came into his world to ask for help.

4)I don't understand why Travis feels the need to assassinate Palentine. Can you help me out on this? Most people think it is because he is linking his emotions towards Betsy to Palentine. But that doesn't make a lot of sense to me. I believe his encounter with Palentine in his cab separates him from Betsy (in this encounter we yet again see Travis completely change to impress those around him). Based on that conversation Palentine should be a symbol in Travis' mind for the change he wants to be initiated. I think this comes down to the conversation which Palentine has in the cab with a campaign manager right before Travis talks to him. I couldn't quite here what they were saying, do you have the exact lines? What I think happened is he overheard Palentine discussing something shady/immoral. He immediately struck up conversation to confirm that it was Palentine, and then fabricated support to make his confirmation seem normal. Later in the movie when he decides to start cleaning up the city himself,he knows he has to start with Palentine because in his mind he is the only person that knows of his corruption. This would make sense because he refers to the assassination as something "only he can do." His unique career as a taxi driver put him in a position to overhear the conversation, and his unique personality gave him the ability to confirm Palentines identity. He was the only person who could do anything to resolve the corruption. Thus it forced him to finally take action and become the hero he had always viewed himself as. It would explain the title of the film a bit more, and why they chose to focus on his profession instead of his mental state in the movie title.

4)Thoughts on the ending?

Mark, you bring up some very interesting points.
It could have very well been that Travis was just lying about his experience in the Marines in the beginning before being hired.

Although, I do think his loneliness and isolation are key driving forces in his violent actions. He does choose to be by himself but attempts to form a connection with Betsy even though it doesn't work. And when she reacts the way she did and rejects him it does reinforce his loneliness. It doesn't change him, you're right. But I think it was insightful to see this temperamental, vicious side of Travis when he bursts into the campaign offices