The first Congress developed this requirement into a simple, 14-word oath:
"I do solemnly swear (or affirm) that I will support the Constitution of the United States."
Oaths of Office For Federal Officials
by Kathy Gill, former About.com Guide
OK, so what does "support the Constitution" actually mean?
Maybe perhaps reading it?
(Or at least, get your "non-essential" staff to do so, for you, and give you the "Cliff Notes" ...)
The Constitution of the United States -- the Preamble.
We the People of the United States, in Order to form a more perfect Union, establish Justice, insure domestic Tranquility, provide for the common defence, promote the general Welfare, and secure the Blessings of Liberty to ourselves and our Posterity, do ordain and establish this Constitution for the United States of America.
The Constitution of the United States --
Amendment XVI
Passed by Congress July 2, 1909. Ratified February 3, 1913.
The Congress shall have power to lay and collect taxes on incomes, from whatever source derived, without apportionment among the several States, and without regard to any census or enumeration.
Note: Article I, section 9, of the Constitution was modified by amendment 16.
The Constitution of the United States --
Article I, Section 8
The Congress shall have Power To lay and collect Taxes, Duties, Imposts and Excises, to pay the Debts and provide for the common Defence and general Welfare of the United States; but all Duties, Imposts and Excises shall be uniform throughout the United States;
To borrow Money on the credit of the United States;
[...]
To coin Money, regulate the Value thereof, and of foreign Coin, and fix the Standard of Weights and Measures;
The Constitution of the United States --
Article IV, Section 1
Full Faith and Credit shall be given in each State to the public Acts, Records, and judicial Proceedings of every other State. And the Congress may by general Laws prescribe the Manner in which such Acts, Records and Proceedings shall be proved, and the Effect thereof.
The Constitution of the United States --
Amendment XIV
The validity of the public debt of the United States, authorized by law, [...] shall not be questioned.
[H/T to Simplify for pointing out this very important Constitution instruction.]
OK, "supporting the Constitution" means raising Taxes to pay for our general welfare and to insure our domestic tranquility, among other things.
OK, "supporting the Constitution" means coining money, lending and borrowing money based on the credit of the United States.
OK, "supporting the Constitution" means if you want to challenge the Full Faith and Credit of the United States, Congressional oath-takers are supposed to "pass Laws" in order 'to tweak' that Full Faith and Credit; (its effects and validations.)
Got That? So-called Congressional public servants? Any questions?
[Note: all emphasis added by the poster, in order to assist 'Cliff'.]