Ballot measures for IRV and STV won in all four jurisdictions in which they were on the ballot in the US midterm elections:
Oakland, California (IRV for all city offices)
Davis, California (STV replaces at-large plurality for city offices*)
Minneapolis, Minnesota (IRV for major offices, STV for some others)
Pierce County, Washington (IRV for nearly all county offices)
All passed quite easily, with the closest being 54% (Pierce County).
* Advvisory measure.