Wouldn't a law like this have to be passed prior to the first election its applied to? I mean, if this is on the ballot in CO this year, and it passes, I can see that it applies to 2008....but not 2004.
There are cases in some staes (I know for sure in IL) that have resolved the issue of concurrent referendum and election. In IL the ruling is that the referendum takes precedence because its results are certified before the elected candidate would be sworn into the office. Since the candidate does not lose an office already held, there is no reason to have that person take an office that is abolished by the voters.