What were the main difference between politics in 1900?
You're still asking about "now". That violates the 20 year rule I cited as a problem in your last post. As it isn't in the title, please edit it out of the main post.
If what you're really asking is 'what were politics like in 1900' the person replying will implicitly draw attention to differences from today. If you call for a comparison with current politics, however, that will just serve to draw in people who want to soapbox about contemporary politics, which is disallowed.