Final answer:
An amendment can be proposed when Congress does not act through either a national convention requested by two-thirds of state legislatures or a two-thirds supermajority vote in both houses of Congress.
Step-by-step explanation:
To propose an amendment to the U.S. Constitution when Congress will not bring forth an amendment, there are two methods:
- Two-thirds of the state legislatures can ask Congress to call a national convention to propose amendments. This method, however, has never been used to date.
- An amendment can be proposed by two-thirds supermajority vote in both the House of Representatives and the Senate.
After the proposal, the amendment must be ratified by three-fourths of the state legislatures to take effect.