The Democrats, the liberals, are incorrigible.  After the terrorist wing of the Democratic Party, the KKK, has been hammered by American society and American norms into irrelevance, now the liberals, no longer able to win at the ballot box, have taken once again to violence as their means of political activity.

The Ku Klux Klan wore white hoods and masks both to create fearsome apparitions and to conceal that they were local townsfolk.  Antifa wear black hoods and face masks both to create fearsome apparitions and to conceal that they are not local townsfolk.  Rather, they have been brought in for the event.  We don't know for sure yet, but it is very likely, given the work of James O'Keefe at Project Veritas Action, that Antifa are the same people going from venue to venue, astroturfing.

Let's take a back-of-the-envelope guess as to what it costs to keep Antifa in business.  We might guess that there are 10,000 Antifa all in, in pockets around the country.  Since they have to be ready for demonstrations at any time, being Antifa is likely their job.  Let's guess that George Soros is funding Antifa and that he pays well above minimum wage – say, $20 per hour.  That is $40K per year – a pretty nice wage, considering that there are no FICA or income tax deductions (we're guessing here).  With expenses, let's round up the cost of an Antifa to $50K.  If there are 10,000 of them around the country, that is an annual expense of $500 million.  No small sum, but well within the resources of Soros, particularly in light of what is at stake: the control of the United States of America.  These are guesses, but as any researcher will tell you, it is better to have a hypothesis than simply to observe.  The hypothesis helps to tell you where to look.

The left cannot gain power through argument.  It has to have dependent constituencies supported by the taxpayer, which is why it wants open borders, or it has to have intimidation.  In some cases, it has both.  The KKK was regional.  Antifa is national, befitting Democratic ambitions.  

The left does not expect Antifa to take over the country, as the Brown Shirts helped the Nazis do in Germany.  The role of Antifa is to poison the well of support for President Trump, to make him seem illegitimate by causing chaos in public spaces at political events.  It's winning through intimidation.  Antifa is the new model of the KKK.