Two things I'd like to see with optical-scan paper ballots (which are IMHO the only way to go): (1) for each race, an explicit "ABSTAIN" choice; and (2) a 'check field' a voter could fill in which indicated how many abstentions there were that the voter hadn't marked. If this field not completed by the voter before a ballot was submitted, the electronic ballot box would either use a printer to mark the ballot with the correct value or else reject the ballot and instruct the voter what to mark. While a ballot with no 'check-field' marks would be either fixed by the box or returned to the voter for correction, and a ballot whose check-field indicated fewer unmarked abstentions than actually existed would returned to the voter for correction (a voter could at that point just mark more explicit abstentions), a ballot whose check-field indicated more unmarked abstentions than existed should be rejected outright. Such a procedure would ensure that no validly-cast ballot--even if it included abstentions--could be altered to reflect any additional candidate selections without becoming invalid.