http://www.nytimes.com/2016/01/29/us/politics/bernie-sanders...
In one sense, it's hard to track the dollars directly. For example, an Anti-Hillary PAC at this point is effectively a pro-Bernie PAC.
On Hillary's page it says outside money spent $2,921,391 for Hillary and $4,413,617 against. So NYTime's reporting is probably out of date since it was before the Iowa vote.
Spending is a bad metric this early anyway since most PACs are just starting to ramp up their spending. Looking at spending + warchests, the Nurses have a couple million to play with while Bush, Clinton, Rubio, etc have 10s of millions. https://www.opensecrets.org/outsidespending/summ.php?chrt=V&...
It's just as easy to believe that OpenSecrets has a reporting delay as it is to believe that the FEC is using some legacy software that doesn't update quickly.
http://www.fec.gov/data/IndependentExpenditure.do?format=htm...
The only workers' rights you have were gained by unions in spite of corporate opposition
His stance is that it's okay because he isn't fund-raising for those PACs, and that they are union PACs, not business. I personally don't see a distinction between unions and corporations.
Full disclosure, I think that Citizens United was decided correctly.