Denver Mayor Mike Johnston and backers of Ballot Issue 2R, a sales tax increase aimed at fueling affordable housing investments and programs, conceded the measure’s narrow defeat early Saturday morning. While it made up ground in later returns after Tuesday’s election, the measure was rejected on 51% of city ballots counted so far, according to the latest results released by the Denver Elections Division on Friday evening. That’s a slight improvement over preliminary results released Tuesday, when the measure had a rejection rate of 52.2%.