I would see the following:
Superman - Taft Republican concerned about corporate fiscal and individual responsibility but wanting individuals to succeed on their own. With his awesome powers could easily become a benevolent despot if he wished to. Ultimately, he is willing to abide by the will of the people and authority if such actions do not compromise his standards. If they do, then he will just check out of the situation. You cannot order him to do anything. Of course he is an illegal alien illicitly adopted by the Kents.
Batman - Hard to say. He can't be put in any box, but I am sure he would be both anti-death penalty and anti-abortion given his strong aversion to taking life. Most readers of him believe that he would do the world an immeasurable favor if he killed the Joker (no Heath Ledger jokes please). I got to think that he would be no fan of the ACLU (unlike what some of the comic book posters said) because he knows no constraints in the protection of innocent life. He will violate any laws and assault any individual if he feels the ends justify the means. He is more than willing to work with cooperative police forces. He is full of internal contradictions.
Original Robin/Nightwing - He is more likely to be a law and order Democrat and a card carrying ACLU member in my opinion. He tries to hold down the darker approaches of Batman.
Green Lantern (Hal Jordan) and Barry Allen (Flash) - Maybe the best we have to offer. Not nearly as full of the internal contradictions of Batman or the alienness of Superman. Hal Jordan is an Eisenhower Republican (except when he went crazy and started destroying worlds). I got to think Barry Allen is a Kennedy Democrat (John not Teddy) only to add some balance.
I have not read much in the DC world since the 80s so these characters may have changed much. They killed off Barry Allen about the time I stopped reading, and Hal Jordan went through an indescribably awful phase in which he became Parallax and the the Specter. I haven't read the stories, and I really don't have much heart to since he was always one of my heroes.