How do I know? I was part of that effort and was in regular email and phone coordination with Sidney Blumenthal. Sidney was the conduit who fed damaging material to me that I subsequently posted on my blog.
The big Kahuna of the anti-Obama dump was the allegation that Republicans had a tape of Michelle Obama in which she used the disparaging term “Whitey.” I published that after being told about the “tape” by Sid Blumenthal. (I learned a few weeks later that the story of the tape actually originated with Media Matter’s David Brock and he confirmed its existence to me in person).
Listening to Hillary Clinton cry crocodile tears over Trump’s questioning Obama’s birth place and eligibility to be President in 2011 as a “racist” attack is the ultimate example that Hillary is cynical and dishonest. Yes, it is true that the words, “Obama is a muslim” or “Obama is not a natural born American” never passed her lips. But it is also true that that people very close to her, such as Sidney Blumenthal, were pushing those stories and trying desperately to promote those memes.