Why did federalist favor the constitution?

Answer 1

Actually, it was the Constitution that favored the Federalists. The Federalists generally favored the U.S. Constitution as providing for a federal nation. As opposed to the anti-Federalists, who favored the confederal model of a "united States" provided for in the preceding Articles of Confederation.

Probably the best answer to why is that a federal model represented a conceptual compromise between that of a confederal state and that of a unitary state.

The Constitution provided for (1) a federated congressional presidential republic; with (2) a supreme but limited federal government; and, (3) States co-sovereign with the federal government; and, (4) to whom residual powers were reserved.

This has become known in U.S. Constitutional law as our federalism.

Answer 2

The Federalists favored the Constitution because at that time, the US was under the governing of the Articles of Confederataion. The Articles gave the federal government extremely limited power, leaving most of the governing up to the states. Since the Federalists wanted a strong federal government, and a Constitution (if written) would grant more control to such a structure, many Federalists were in favor of such a document. The Anti-Federalists were against this for the same reason.