City Councilman and Manhattan Borough President candidate Robert Jackson is getting an endorsement today from the Local 147 Sandhogs Union, a group of tunnel diggers. It’s the second union endorsement for Jackson in the 2013 race. He’s already been endorsed by former Mayor David Dinkins and by IATSE Local One, the Stagehands Union. The second union endorsement comes after City Councilwoman Jessica Lappin rolled out her first union endorsement for the 2013 borough president’s race. Jackson is expected to face not only Lappin, but also City Councilwoman Gale Brewer and former Community Board 1 Chair Julie Menin.