<i>The UAW takes in about a third of a billion dollars a year in union dues ...</i><p>Drops in the bucket compared to what their corporate issue adversaries take in.  For instance, the minimum revenues of any Fortune 500 company right now is measured in the billions (profits at around half a billion).<p><i>Currently unions are prohibited from contributing directly to candidates due to being tax exempt entities, but that doesn't stop them from spending tens of millions of dollars during election campaigns to support the candidates they favor.</i><p>And you can say the exact same thing about corporate interests (both individual corporations and their "unions" of trade associations).  The only difference is that corporate interests have literally orders of magnitude more money available to pursue their agenda, as well as a disproportionate set of connections in Washington.