Backers of Initiated Ordinance 300 (I-300), a Denver ballot measure intended to permit cannabis consumption in certain private places in order to reduce it in public spaces, announced Tuesday that it had received several major political endorsements. The Democratic Party of Denver, New Era Colorado, State Sen. Irene Aguilar of Denver, and State Rep. Jonathan Singer have joined more than 100 local businesses and organizations that are encouraging Denver residents to vote “YES” on 300 to establish…