Antifa is a decentralized, leaderless confederation of chapters that operate semi-secretly and often differ in strategy. Their oldest chapter, located in Portland, Oregon, has specific criteria for what it defines as fascism, with an overriding characteristic of any such movement being that it uses violence to achieve its goals.
The group explicitly decries the overuse of the term to describe "any idea that is authoritarian, right-wing, or even just disliked." Neither their website nor the umbrella website for Antifa, called the Torch Network, makes any explicit mention of the Republican Party, President Trump, or "MAGA"-related themes as a focus of its attention.