The consensus needed to amend the U.S. Constitution is exceptionally difficult to reach. Proposing an amendment requires many votes from both parties to reach two-thirds support in the U.S. House and Senate, or for a never-been-done amendment convention applied for by two-thirds of state legislatures. Ratifying an amendment requires approval by three-fourths of state legislatures or conventions in three-fourths of the states. Either path means appealing to diverse state legislators or voters. Constitutional language differs from statutes. The Constitution is mostly broad principles that are applicable across the centuries. Congress gives them form for contemporary circumstances through implementing legislation that it updates through the normal statutory process. Notwithstanding ambiguities, constitutional language puts guardrails on congressional action. The 27 existing amendments range from one to several principles, but most BBA proposals are far longer and more detailed. The Business Cycle BBA and especially the Principles-based BBA are most in character with amendments that have succeeded so far. Finally, Article V of the Constitution sets out the amendment process. Its general language raises many questions that Congress could answer through implementing legislation.