Donald Trump has said that as president he’ll promote a constitutional amendment setting term limits on members of Congress. Whatever you think of the merits of the amendment (I can think of good arguments both for and against), his proposal shows a certain ignorance of the Constitution, as similar proposals for constitutional amendments by candidates of both parties have in the past.
The Constitution gives the president no role whatever in amending the Constitution. Amendments can be proposed by Congress or by state legislatures, or by a constitutional convention called pursuant to Article V. They can be ratified by votes of three-quarters (currently 38) of the state legislatures.
The president has no veto in any of these processes. His or her official powers are no greater than that of the ordinary citizen casting votes for members of Congress or state legislatures. The president may have a louder voice than most, and in some circumstances a more effective one. But he or she has no official role.
