For the most part, superheroes tend to exempt themselves from partisan politics. Except in rare cases -- like 2008's super-weird DC Universe: Decisions special that literally broke down the political positions of several DC heroes -- we're left to imagine whether Bruce Wayne "felt the Bern" or if Hal Jordan voted to Make America Great Again. However, it's fun to examine the philosophies of particular heroes and imagine where they'd fall on the political spectrum. Or, in the case of the two-party system in U.S. politics, whether they're a Democrat or a Republican.
For the purposes of this article -- and to get a good discussion rolling -- let's look at Superman, and go over the many reasons why he would likely vote for a Democratic candidate in a U.S. presidential election. For many of us, it's obvious that Superman is a Democrat, but for those who might be interpreting Jerry Siegel and Joe Shuster's message in a different way, let's run down why he leans left.
The first-ever glimpse of Superman, on the cover of 1938's Action Comics #1, was an image of him flipping a car and scaring the hell out of a capitalist "suit," evoking a powerful anti-economic inequality message. As discussed at length in Grant Morrison's Supergods manifesto, the image signifies a rejection of greed, and defiance against the wealthy.
Superman would have no problem paying taxes -- something Republicans take issue with, to say the least. The principle behind taxes, at least in their modern form, is to offer one's fair share for the betterment of a community. While Clark Kent undoubtedly pays taxes as a reporter for The Daily Planet, Superman's contributions come in the form of civil service. As evident time and time again, the Man of Steel wholeheartedly believes in something usually associated with Spider-Man: With great power comes great responsibility.
Superman feels an inherent responsibility to offer his "wealth" (in his case, superpowers) rather than viewing his good fortune as something deserved and kept for himself. Superman's prerogative to use his fortunate position to help others would, no doubt, make him side with a single-payer healthcare option. Rather than believing healthcare -- or the right to maintaining a healthy life -- is something completely under the responsibility of an individual, Superman would view paying taxes for the sake of healthcare for all as a no-brainer. In short, Superman would be willing to forfeit choice, or liberty, in favor of life.
Nationalism vs. Globalism
While nationalism isn't something inherently Republican, it's often championed by the party as part of an economic message, especially in recent years. Like how Democrats are generally left to advocate for social justice, Republicans are there to preserve national identity. While Superman is often associated with "Truth, Justice and the American Way," he's proved time and again that he is not for American exceptionalism, as discussed at length in editor Mark D. White's Superman and Philosophy: What Would the Man of Steel Do?
Superman wasn't always championing "the American Way." That addition to the character's motto was popularized for the 1950s serials starring the late, great George Reeves, but was first added in the 1940s as a means to stir patriotism as the United States entered World War II. "The American Way" was represented as the "good" in a fight of "good vs. evil," not necessarily as an American exceptionalist message.
Furthermore, in DC Comics' controversial 2010-2011 storyline "Grounded," Superman renounces his American citizenship. Sending a message that he disagrees with the (then-) current political climate, Superman set out to reconnect with the grassroots of America and champion a more globalist, internationally inclusive message. This shows how Superman is prepared to ditch "the American Way" part in favor of Truth and Justice.
While Superman is more than willing to be a "Boy Scout" for President Reagan in Frank Miller's The Dark Knight Returns, it's indicated in the story that Superman (at least with that wink upon the big reveal at the story's end) is more for what's right in general, rather than for what's right for the American cause.