Obviously, it’s not just Ayanna Pressley who’s interested in Ed Markey’s U.S. Senate seat. There’s a whole bunch of Dems angling for a shot should the 79-year-old Markey falter in coming days, weeks and months. Potential Dem candidates/challengers include Jake Auchincloss, Seth Moulton, Andrea Campbell, Michelle Wu and, of course, Pressley, as the Herald’s Joe Battenfeld reports. … The Globe’s Joan Vennochi was writing about the Auchincloss angle a couple of weeks ago.