[jellybean]

A Constitutional Amendment would be required to elect the President by popular vote.

Article II

Section 1. The executive power shall be vested in a President of the United States of America. He shall hold his office during the term of four years, and, together with the Vice President, chosen for the same term, be elected, as follows:

Each state shall appoint, in such manner as the Legislature thereof may direct, a number of electors, equal to the whole number of Senators and Representatives to which the State may be entitled in the Congress: but no Senator or Representative, or person holding an office of trust or profit under the United States, shall be appointed an elector.

[Calpernia]

They [states] are pre pledging the electoral votes. They don’t need an amendment to do that. There is no law stating how the electors cast their vote.

Here is the links that go to each’s states legislatures

http://www.nationalpopularvote.com/pages/statesactivity.php