The U.S. Constitution, Article IV Section 4, guarantees to 'every State in this Union a Republican Form of Government.

FORBES: Fact and Comment

The military is the most centralist of all institutions and permanent alliances, standing armies, and the permanent military footing which tends to accompany such a policy is injurious, he said, to our republican form of government.

FORBES: Benjamin Netanyahu Vs. Barack Obama, Part One

It is therefore not surprising that whether to make provision for impeachment of the president became the focus of contention, especially in the context of concern whether, in our new republican form of government, the legislator ought to be entrusted with such a power.

CNN: Transcript: White House Counsel Ruff's opening statement