The initiative would add a new section 13 to Article VII of the Colorado Constitution. Section 13 would provide for proportional division of presidential electors. The initiative states explicitly that "This section [i.e., section 13] shall be effective on and after November 3, 2004." See numbered paragraph (9) of the initiative, the text of which may be found at
http://www.lawanddemocracy.org/amend36.html.

The initiative does provide that it is intended to have retroactive effect so as to apply to the election held on November 2. But I believe it cannot have that effect. Article II, sec. 1, cl. 4 provides that "The Congress may determine the Time of chusing the Electors ... ." Congress has done so in 3 U.S.C. section 1:

"The electors of President and Vice President shall be appointed, in each State, on the Tuesday next after the first Monday in November, in every fourth year succeeding every election of a President and Vice President."

Thus Colorado must "chuse" its electors on November 2. Colorado will do so by vote of its people on November 2. The choice will be made under the existing "winner take all" approach, which will still be in effect on that date even if the initiative passes. The state could only choose electors after November 2 if there was a failure to choose them on November 2 (see 3 U.S.C. section 2) or if an elector position becomes vacant (see 3 U.S.C. section 4).

By its terms, the new section 13 added by the initiative (if it passes)would not go into effect until November 3. The only way it could be given effect for this election would be for it to have the effect of "un-chusing" the electors that were chosen on November 2 and replacing them after that date with new electors. The federal statute, enacted pursuant to Art. II, sec. 1, cl. 4, does not permit that.

Perhaps there is a feature of the Colorado Constitution providing that initiative measures cannot go into effect until the day after an election. Otherwise I don't understand why the initiative drafters would have drafted it with a November 3 effective date. But in any event, that is the effective date, and I do not see how it can be given retroactive effect without violating federal law.