Green Arrow is pretty leftie, but are there any other characters who have strong political views?
Wasn’t Superman pretty anti-NAZI?
Green Arrow was paired with both Green Lantern and Hawkman at various times with them being the conservative counterpoint to his liberalism.
Hawkman being the better foil for Ollie, being more the conservative counterpart to his strong beliefs. Hal’s more moderate than either of them.
I think we can say for certain Batman’s big on gun-control.
Animal Man is into animal rights.
Freedom Beast (the replacement for B’wana Beast who I’m not sure is even in continuity any more) was actively working against apartheid.
Well, there were Hawk and Dove. Hawk was a hawk when it came to the use of force, and Dove was a…hmm, let me try to remember what his views were…oh, right, he was a dove.
And while Hawkman is generally conservative he’s also an extreme enviromentalist.
Even in comic book characters there are no simple politics.
What party did Lex Luthor run with?
Captain America is thought to have strong pro-American leanings.
Howard the Duck once ran for president as the candidate of the All-Night Party.
The Punisher practices vigilante justice – but I think that’s more of a personal lifestyle choice than a political ideology.
During the Cold War there were lots of Commie supervillains – the Black Widow (originally a KGB agent), Dynamo, the Red Ghost. And Iron Man got his start (in Vietnam) as a Commie-fighter.
The Red Skull is a Nazi.
Marvel once had an internationalist superhero/villain called “Flag Smasher,” but they never did much with him.
Any superhero who is also a god (Thor, Hercules) is probably a religious traditionalist. 
I’d say that Ozymandias from Watchmen was pretty political, in a way.
I suspect that Super President had some political views of his own.
Wally West (Flash III) is a union boy, pro-death penalty, and pro-gay rights, at least by association with the Pied Piper, a sometimes gay activist.
Wonder Woman is strongly for women’s rights, the environment, and peace in general.
Black Manta was sometimes portrayed as a radical Black separtist.
I’m pretty sure Luthor was independent.
Magneto is relatively pro-mutant.
Dr. Doom has strong Pro-Doom leanings.
The Great Machine (from Ex Machina) is pro gay rights. He’s also super-cool, imho.
Aquaman is a Royalist (duh), and a radical environmentalist.
As is Namor.
What is it with the goldfish boyz, anyway?
Prez obviously had political leanings, most clearly in lowering the voting age and in environmental action.
Badger and Butcher (both written by Mike Baron) have strong Libertarian leanings.
Captain America seems to be a mouthpiece for whomever writes him. Englehart wrote him as a Democrat, and Shooter wrote him as a Republican.
Iron Man is pretty coy about his political affiliations, but he seems pretty much in line with the Republican party. Wasp and USAgent, too. The Wolfpack were all pretty hardcore conservative.
Ultimate Cap, on the other hand, is as right-wing as you can get without tipping over into psychosis. Millar, I believe, is not.
Millar is doing his best to write him as a charicature…but not succeeding.
As mentioned, Wally West is pro-Death Penalty, and in a recent issue of Flash, we’re told that Wonder Woman and Barry Allen are/were both pro-Death Penalty.
And Batman has somewhat strong views on crime.