From the Washington Post:

So far this year, $24.7 million in independent [political] spending has been reported to the Federal Election Commission, campaign filings show. Unions have spent $9.7 million, or 39 percent of the total, compared with $6.4 million, or 26 percent spent by individuals and $3.4 million spent by corporations.

This comes as no surprise. Nor does the fact that Democrats want to tip this lopsided balance even further by exempting unions from most of the rules of their new anti-free speech law, the DISCLOSE Act.