AntiFa is a political movement that opposes fascism. There is no evidence that AntiFa is connected to the Democratic Party.
The vast majority of AntiFa militants are radical anti-capitalists who oppose the Democratic Party. However, rumors have surfaced in the recent past connecting AntiFa to President Joe Biden and/or the Democratic party. In August 2020, and many times after, the URL of AntiFa, "antifa.com" redirected to Joe Biden's official website, "joebiden.com", and to "whitehouse.com", a day after Biden had declared President.
AntiFa's site and can be redirected to any other website and redirection does not mean it's connected or affiliated. This does not mean that AntiFa is connected to Democrats or to Biden. There is no evidence to support this connection.