They have in the past have been wildly unsuccessful. This is an issue for every rally and it seems it is handled rather effectively. The few that have made it into the rally venues in the past have been "dealt with" by the crowd and security.
I remember seeing a number of ANTIFA communists, showed up in some California town, and got their a$$e$ handed to them. I doubt they will show up there again.
https://newshourfirst.com/2020/06/03/antifa-members-get-the-ever-living-daylights-beat-out-of-them/