Your blog is your own, you can do what you want with it. That said, bear in mind that if you do get political, you will alienate a significant proportion of readers. If I read a blog post supporting Trump, for example, I'd never buy or read a book by that author, not only in protest, but because I'd assume the writer's an idiot.
You can keep politics and writing separate by writing two blogs, if you have the energy for that much unpaid writing. Or you could confine your rants to FB or another "friends only" venue. I have two FB pages: my personal one, for friends and family, where I rant nonstop, share political information, and unfriend anyone who voted for the devil. My author FB page is all about my books, and publishing in general. Keeping them separate lets me vent without losing readers.