National Popular Vote (NPV) Initiative: Direct Election of the President by Interstate Compact [open pdf - 1MB]
From the Summary: "The National Popular Vote (NPV) initiative proposes an agreement among the states, an interstate compact that would effectively achieve direct popular election of the President and Vice President without a constitutional amendment. It relies on the Constitution's grant of authority to the states in Article II, Section 1 to appoint presidential electors 'in such Manner as the Legislature thereof may direct.... ' Any state that joins the NPV compact pledges that if the compact comes into effect, its legislature will award all the state's electoral votes to the presidential ticket that wins the most popular votes nationwide, regardless of who wins in that particular state. The compact would, however, come into effect only if its success has been assured; that is, only if states controlling a majority of electoral votes (270 or more) join the compact. At present, 15 states and the District of Columbia, jointly accounting for 196 electoral votes, have joined the compact."
CRS Report for Congress, R43823
Congressional Research Service: https://crsreports.congress.gov/