Heavy Hitters

Top All-Time Donors, 1989-2012

(Influence and Lobbying donations by Companies/Groups, and what percentage went to each political party)

See data at this link:
Top All-Time Donors, 1989-2012 | OpenSecrets

I'd be far more concerned about the "expediency" (or "what's in it for ME) of No. 3 ranked AFSCME - American Federation of State, County, & Municipal Employees.

Of the $46.3 million AFSCME donated to candidates, 94% of it went to Democrats and 1% of it went to Republicans......

Or....

Eleventh (11th) ranked American Federation of Teachers, who donated $31.8 million of which 90% was donated to Democrats, and 0% (zero percent) to Republicans.

On the whole, corporations gave similar amounts to both parties.