If it was "fucking nothing," I doubt they would bother. Rather, they look at it as a good investment that pays off. I know this to be true because of the intense earnestness with which they encouraged me and so many others to donate. Of course, maybe all they wanted was the charitable contribution deduction, that could be true. But I listened to many talks by officers of BigCorp in which they talked about the importance of these contributions to swerve legislation at the local, state, and federal level to their favor, most often to reduce the cost of doing business in the many states in which this particular BigCorp did business.

You misunderstand. Political financing in the US is very complex; all I'm saying is that the direct donations by corporate PACs to individual candidates is utterly trivial.

Look at this list: http://www.opensecrets.org/pres12/contrib.php?id=N00009638

"This table lists the top donors to this candidate in the 2012 election cycle. The organizations themselves did not donate , rather the money came from the organizations' PACs, their individual members or employees or owners, and those individuals' immediate families."

So if we look at Microsoft, $800k went from Microsoft and related entities to Obama's campaign. That's a lot of money, and I have no doubt it bought real influence with Obama. But out of that $800k, at most $5k was the money that went directly from Microsoft's PAC to the Obama campaign. And that's well...nothing. It is 0.625% of the total amount given by Microsoft, 0.0007% of the total amount given to candidate Obama.

I have no doubt that BigCorp was very insistent about your contributing to the PAC; but they had no intention of using more than the barest fraction of that money to donate to the campaign of individual politicians. They couldn't, even if they wanted to. They would have been intending to spend it on much more effective (and unregulated) channels.