You forget how good Taxi Driver is. You see the references, you hear the imitations, you read the dopey fan theories and you forget that this film is a taut, driven piece of filmmaking, a movie as troubling and thrilling as any that has come since.
As DeNiro gets older you forget the steel in his eyes as Travis Bickle; this isn't acting, he has summoned another human being to live through him. It is complete in the way few performances have ever been, a character who stalked off the movie screens and into our culture for eternity. It takes a powerful performance in a truly unforgettable film to fuel a future presidential assassination attempt, after all.
Travis Bickle stalks the streets of New York City like a shark, never stopping, his thick yellow cab slicing through curtains of steam like a knife. He sees the city around him as a cesspool, a shitheap that can yet be saved. And who can blame Bickle? In the middle of the 1970s New York City wasn't in decline, New York City was a festering corpse. The year before Taxi Driver came out the famous New York Daliy News headline "FORD TO CITY: DROP DEAD" summed up the federal government's opinion about the city's malignant economic situation. A year later the Son of Sam would stalk the streets, and the great blackout would lead to rioting and fires that burned down sections of the city. Crime was out of control, the subways weren't safe and everyone had basically ceded Central Park to muggers, rapists and junkies. Times Square, full of pimps, hookers and con men, had become the black heart of the city.
But while Travis Bickle thinks he's better than the scum, that he's the rain that will wash them off the streets, the reality is that he is of them. He wishes he wasn't, he wants to be the kind of man who could be with Betsy, but he's unable to understand why you don't take a woman to a porno movie (he's so of the world of squalid Times Square it doesn't even occur to him that there are other kinds of movies). Sport recognizes him as one of his own kind; as a modern day riff on Ethan Edwards, Travis Bickle is just as savage as the savages he hates. It's what makes the ending of Taxi Driver such delightful irony - while Ethan is left outside the homestead, never able to come home, in 1976 the monster becomes the hero.
A monster is exactly how the trailer for Taxi Driver positions Travis Bickle; watching this trailer it's easy to realize that no one foresaw Bickle becoming a weird kind of counterculture folk hero. Nobody thought his face would hang on a thousand dorm room walls, or that his "You talkin' to me" speech (improv'ed by DeNiro, possibly based on something he heard Bruce Springsteen say!) would be something wannabe tough guys would practice to themselves. The trailer intriguingly hides the nature of Jodie Foster's role, although I imagine that sensibilities at the time would have blanched at a preview talking about child prostitution too openly (although you can easily infer it from the first scene in the trailer). In a lot of ways this helps maintain the film's inherent mystery - you or I might use Iris as the basis for a synopsis of Taxi Driver, but the trailer plays up the Betsy angle and kind of obscures the Palantine aspect. You look at this trailer and expect a slightly political thriller, when the reality is that Travis Bickle doesn't have a single political thought (reflecting Arthur Bremer, the man who paralyzed George Wallace, who in his diaries wrote that he wanted "to do SOMETHING BOLD AND DRAMATIC, FORCEFUL & DYNAMIC, A STATEMENT of my manhood for the world to see."
That ends up being the most intriguing aspect of Travis Bickle, and why people ended up identifying with him. He's a monster almost in the Universal tradition - he's reaching out for connection but his way of doing it is distastrous and deadly. He's Frankenstein's Monster throwing the girl into the lake, except that in the cynical worldview of Paul Schrader and Martin Scorsese it turned out his target deserved it, and the Monster becomes the hero.