Superman is not a republican, Mr. Serrano.

Actually, I’ll let Jim Henley counter that stupidity, he does it so very well:

The history of Superman’s politics is genuinely interesting. In Action Comics #1, his first appearance, he’s a dedicated isolationist. His enemies are a Senator and a lobbyist pushing a bill that will “embroil us with Europe.” He solves the problem by, well, kidnapping them, dumping them in the middle of a pointless war between two Central American nations.

His best sentence comes when he responds to Serrano’s charge that Spiderman is an independent with libertarian leanings:

“With great power there must come great responsibility” is as pure a distillation of Great-Society/New-Frontier liberalism as you’ll find. It’s like, find Objectivism on your political map; now go to the opposite spot.

Of course, it’s fantastically hard to pin any specific political leaning to characters who change creative hands several times a year:

(T)he correct answer is that all superheroes have the politics of whoever is writing them at the time.