I spent all day today at the OFA office in West Denver calling voters identified by the campaign as needing to enclose a copy of their ID with their mail ballot in order to have their votes counted. Mail voters with a DL who were identified through cross checking with the DMV as residents of CO do not need to include an ID with their ballots. However, mail voters without DLs, or mail voters who do have a DL but whose names would not correlate with DMV records because their names were not properly spelled out by the registrars office in placing them on the VR roll, or mail voters who simply live in counties where the county clerk did not do due diligence with DMV records, will not have their votes counted unless they enclose a copy of an acceptable ID. Incredibly, many of these voters were not so alerted in the instructions which were enclosed with their mail ballots - indeed they were often told no ID was necessary in the general instructions included with their ballots.
So heads up -- if you are voting a mail ballot in CO, and have any doubts, don't take any chances of having your vote rejected. Include a copy of your DL, student ID (picture only), utility receipt with your name and address, Colorado ID, bank account statement, passport, pay statement from work. And pass the word around if you are in CO. If you are affected and have already sent in your ballot, you can fix it by going to an early vote location with a copy of your ID and explain why you are turning it in. Or you can mail a copy of your ID to the clerk's office with a letter explaining the same.