The 2012 Republican Party platform was formalized today at the Republican National Convention in Tampa, FL. In it, the GOP takes a firm stance against instituting a national popular vote scheme.
From the official platform document:
We oppose the National Popular Vote Interstate Compact or any other scheme to abolish or distort the procedures of the Electoral College. We recognize that an unconstitutional effort to impose “national popular vote” would be a mortal threat to our federal system and a guarantee of corruption as every ballot box in every state would become a chance to steal the presidency.
The National Popular Vote Interstate Compact includes 8 states and the District of Columbia, as of April 2012. It is an agreement among states to award their electoral votes to the winner of the national popular vote. Until the compact is joined by states with a majority of electoral votes, all states continue awarding electoral votes according to standing rules.
States that have passed legislation joining the compact are Vermont, Maryland, Washington, Illinois, New Jersey, District of Columbia, Massachusetts, California and Hawaii.