A Douglas County election official today vowed to ensure a clerical error that led to a ballot mix-up won’t happen again, while county residents were returning ballots at high rates, planning election night parties and making last-minute phone calls to get out the vote. After long campaigns by the presidential candidates and congressional, legislative, city council and mayoral hopefuls, Election Day is finally here. “I can’t imagine anybody that is still undecided,” Douglas County Democratic Party Chairman Dean Byers said today. “I do hope that people go out and vote today.” The Douglas County Democratic and Republican parties are both …