No. Because they are the biggest buyers of influence on the hill. It has absolutely nothing to do with having a bunch of people, just a bunch of money.
13 out of the biggest 20 donors are unions. http://www.opensecrets.org/orgs/list.php?order=A
13 out of the biggest 20 donors are unions. http://www.opensecrets.org/orgs/list.php?order=A
Donations are only one small way that money influences the hill. If they were as effective as lobbying, you wouldn't see 10X the money being spent on that.