Changing the Constitution requires 2/3rds of each house of Congress. [0] If there were such a strong majority for reform, the reform would already be law.
[0] Amendments also require majority agreement in both houses of 3/4ths of the state legislatures.
That's one out of two ways to change the constitution. It can also be initiated by the states without the involvement of Congress. See [1]. This is the strategy being adopted by the Wolf PAC[2] which is seeking to pass an amendment abolishing corporate personhood & publicly financing elections.
[0] Amendments also require majority agreement in both houses of 3/4ths of the state legislatures.