Okay, but honestly, who decides who they vote based on an endorsement. I'm just saying.
Lots of people. Why would they care about endorsements otherwise? I'm sure having a man as well respected in the Latino/Hispanic community will cause some people to rethink their views about Obama.
Hispanic Americans and African Americans have a long history of, well, racism. Obama wanted his endorsement to prove to those voters that the racism should be long past.