It is, I gather, fairly common for corporate donors to give money to both candidates in some two candidate races. Assuming that is correct, the question is why.
Both donations can't be intended to influence the outcome of the election, since they push it in opposite directions, so presumably the purpose is to buy influence with the winner. But doesn't the donation to the loser reduce the donor's influence with the winner, just balancing an equal donation to the winner?
I can see two possible answers. One is that the information is not always public, so the winner may not know about the donation to the loser. I don't think that's been possible in recent elections, but I'm far from expert on the subject.
The other possibility is that the money isn't intended to be spent on the election. It's my understanding (those who know more are welcome to correct me) that, under some circumstances, a candidate who retires is allowed to keep the balance of past campaign donations. If so, one would expect the pattern of donating to both candidates to be most common when at least one of them is near the end of his career.
Which suggests some interesting possibilities for research.
P.S. A commenter informs me that my fact is not a fact, that what is actually happening is that donations by employees of a firm, some of whom support one candidate and some another, are being misinterpreted as donations by the firm.