In 2010 Reddit was center-left, with a high degree of variance between subreddits.
Today it is a far-left echo chamber in most large subreddits.
The process of change was gradual. Like all echo chambers it is a result of distillation, with marginal moderate users progressively leaving in response to seeing the shrinking frontier of acceptable discourse.
Early Reddit had a philosophically libertarian majority (or at least, a significant percentage) and a demographic of mostly STEM-oriented, bookish, nerdy dudes from 18-40. Ron Paul was a popular political candidate. "Socially liberal, fiscally conservative" was a common refrain, although in 2008 that usually meant supporting gay marriage and wanting legal marijuana. People were skeptical of big corporations and big government alike, but had genuine belief that technology was changing the status quo in positive ways (remember when Google was a startup and "Don't be evil" felt earnest). The wars in Iraq and Afghanistan were unpopular, but a big chunk of the criticism focused on ways the PATRIOT act invaded individual privacy and the wastefulness of DHS spending. Open source software and filesharing were discussed as philosophical stances and acts of resistance against entrenched powers. Race and gender were rarely discussed as being particularly important.
Writing this made me realize not just how different Reddit was, but also the issues of the time and the ways they were thought of and talked about. It's almost hard to map onto contemporary parties, policies or issues.
That’s like a frog saying the water isn’t getting warmer.