Federalists, those who identified with federalism as part of a movement, were the main supporters of the Constitution. They were aided by a federalist sentiment that had gained traction across many factions, uniting political figures. This does not mean there was no heated debate over the Constitution's drafting, however. The most zealous anti-federalists, loosely headed by Thomas Jefferson, fought against the Constitution's ratification, particularly those amendments which gave the federal government fiscal and monetary powers.
The Anti-Federalists proved unable to stop the ratification of the US Constitution, which took effect in 1789. Since then, the essays they wrote have largely fallen into obscurity. Unlike, for example, The Federalist No. 10 written by James Madison , none of their works are mainstays in college curricula or court rulings.  The influence of their writing, however, can be seen to this day - particularly in the nature and shape of the United States Bill of Rights. Federalists (such as Alexander Hamilton, in Federalist 84) vigorously argued against its passage but were in the end forced to compromise.  The broader legacy of the Anti-Federalist cause can be seen in the strong suspicion of centralized government held by many Americans to this day.
So I would argue, in the spirit of Thomas Jefferson and George Washington, that while The Federalist Papers are among the best essays ever written on representative government, they would not be as good as they are, or as many essays as there are, if it were not for the persistent critique of the Antifederalists who helped define the American conversation over what should government do, which level of government should do it, and which branch of that level of government should do it. Those questions are what the Essential Antifederalists bring to the conversation.