Mark Schmitt, writing for The New Republic, comments here on Americans Elect, and then goes on to recommend Instant-Runoff Voting in presidential general elections. He also recommends that states permit fusion (i.e., letting two parties jointly nominate the same candidate).
Schmitt says only five states permit fusion, although he does not name them. Actually more states than that permit fusion. They are Connecticut, Idaho, Massachusetts, Mississippi, New Hampshire, New York, Oregon, South Carolina, and Vermont; and Pennsylvania permits it for certain partisan offices. In Massachusetts, New Hampshire and Vermont, fusion only can be accomplished via write-in votes in primaries.
But Schmitt also understates the number of states that permit fusion for President. Approximately half the states permit fusion for president. This is because so many state anti-fusion laws are worded to only apply to candidates nominated in direct primaries. But presidential elector candidates are not nominated by primary in any state; generally presidential elector candidates are nominated in state conventions.