Sup. Chris Daly appears to be coming up just short in a power play to force affordability standards on the 10,000 housing units that Mayor Gavin Newsom, Lennar Corp., and other top power brokers are trying to build through a June ballot measure. Daly has been working with Bayview-Hunters Point activists — including those with People Organized to Win Employment Rights (POWER) and Center for Self-Improvement — to craft a ballot measure that calls for rental housing in the area to be affordable by those making half the city’s median income or less and for housing sales to be affordable by those at 80 percent of the median income or less. Daly needs the signatures of four supervisors by 5 p.m. today to place it on the ballot, but right now he only has Sup. Ross Mirkarimi. Supporters of the measure just minutes ago lined up to testify during the public comment portion of today’s Board of Supervisors meeting, citing the dire need for affordable housing to stem the black exodus from the city, while the African-American ministers who have been close to Lennar and Newsom urged the supervisors not to sign it. While Daly tells us there’s still a chance to get signatures from Tom Ammiano and/or Gerardo Sandoval (who at one point, Daly said, seemed inclined to support it but may have gotten worried about how it might affect his run for judge at the same time), but it doesn’t look good. Lennar representatives and their allies have been circulating through City Hall since the measure was completed on Friday, lobbying hard against it. Now, activists may have to gather signatures if they hope to qualify the measure for the June ballot.