On November 14, 2019, DC for Democracy had an endorsement vote for the Council Ward 2 race in the 2020 primary. We followed our the process prescribed in our bylaws, which gives voters the option of indicating a second choice to be used if their first choice has been eliminated. A candidate must meet a high threshold of two-thirds support to be endorsed, and all ballots with votes continue to be counted as part of the total for that calculation even after all the candidates on them have been eliminated. Effectively, "No endorsement" acts as a special candidate that can never be eliminated, acts as the last choice for every ballot, and wins by default if no one else reaches the threshold.
The animation below explains how the process worked in this case. Each box represents a ballot and contains one or two choices indicated by color and initial. You can use the three buttons to advance one step, to run through the entire process, or to reset the process to the beginning. You can control the speed with the slider.