The Anti-Federalists were opposed to the ratification of the 1787 United States Constitution because they feared that the new national government would be too powerful, endangering individual liberties in the absence of a bill of rights.
Patrick Henry was adamantly opposed to the new constitution because it established a weak national government. The main debates at the constitutional convention were not about the basic ideas of the new government, but about how they would be implemented.
He refused to attend the Constitutional Convention because he feared it was a plot by the powerful to build a strong central government over which they would rule.