The President of the United States is not a man, but an office occupied by a man. And the office carries only those powers enumerated in Article II of the Constitution of the United States.
§1 The Executive Power shall be vested in a President of the United States of America. . . . §2 The President shall be Commander in Chief of the Army and Navy of the United States, and of the Militia of the several States, when called into the actual Service of the United States; he may require the Opinion, in writing, of the principal Officer in each of the executive Departments, upon any subject relating to the Duties of their respective Offices, and he shall have power to Grant Reprieves and Pardons for Offenses against the United States, except in Cases of Impeachment. He shall have Power, by and with the Advice and Consent of the Senate, to make Treaties, provided two thirds of the Senators present concur; and he shall nominate, and by and with the Advice and Consent of the Senate, shall appoint Ambassadors, other public Ministers and Consuls, Judges of the supreme Court, and all other Officers of the United States, whose Appointments are not herein otherwise provided for, and which shall be established by Law: but the Congress may by Law vest the Appointment of such inferior Officers, as they think proper, in the President alone, in the Courts of Law, or in the Heads of Departments. §3 He shall from time to time give to the Congress Information of the State of the Union, and recommend to their Consideration such Measures as he shall judge necessary and expedient; he may, on extraordinary Occasions, convene both Houses, or either of them, and in Case of Disagreement between them, with Respect to the Time of Adjournment, he may adjourn them to such Time as he shall think proper; he shall receive Ambassadors and other public Ministers; he shall take Care that the Laws be faithfully executed, and shall Commission all the Officers of the United States.
Please note (and this is very important) that Article II does not give the President any power to set domestic policy. It states only that he shall recommend to Congress' consideration such measures as he shall judge necessary and expedient. Recommend to their consideration.
The power of the President to propose legislation is exactly the same as the power of any other citizen who is not a member of Congress. I may write to my (or any) Congressman tomorrow and propose a Constitutional amendment repealing the Commerce Clause. I can recommend such a measure to Congress' consideration. This is the same thing Article II says the President may do. The only difference is that the President is required to do so, and I am not. His suggestions may carry more weight with Congress, but they carry no greater legal authority. Article I §7 gives him a veto power, but this is a power of negation, not creation.
Therefore, when Presidential Candidates throw around domestic policy suggestions like national health care, mandatory public service, or writing God into the Constitution, do please remember that the President can suggest legislation all he wants, but the responsibility for enacting it lies with Congress.
This is just electioneering. The President does not have the power to compel Congress to consider any measure, and he does not alone have the power to enact such changes. Therefore, the domestic policies espoused by Presidential Candidates must always weigh less heavily on any election choice calculus than their espoused policies concerning the actual powers of the Office of the President: foreign policy, judicial appointments, and the faithful execution of the laws. Statements about domestic policy may suggest how a Presidential Candidate would carry out his Constitutional powers if he were elected, but the power of the Office to influence domestic policy is limited to the appointment power and the veto power.
The appointment power is a power of creation. No person may hold judicial office unless he first be appointed by the President. Congress holds the power of negation (the confirmation power). Furthermore, Federal judges sit for life, and can only be removed by impeachment. Vetoes may be overridden, and legislation may be easily amended or repealed. The appointment power is, therefore, the President's strongest tool for affecting domestic policy.
Certainly Huckabee's statements express an appalling enmity for the Constitution and for individual rights. But the actual proposal to amend the Constitution is not what makes Huckabee so dangerous.