Even if all the hidden money funneled into campaigns through private 501(c) organizations had come from businesses — unlikely given the contributions by noncorporate groups like Planned Parenthood and the N.R.A. — corporate spending would not reach $400 million, still a small share of the total.

Perhaps this should not be surprising. For companies, spending on elections can be risky. Business executives might prefer lobbying, where they spend far more than on campaign contributions, not because the limits are more relaxed but because swaying legislators on both sides of the aisle is more effective at getting what they want. And such lobbying is less likely to kindle anger among consumers, shareholders and other constituents than spending to change the outcome of elections.

“While Citizens alters the ability of corporations to contribute to campaigns, it does not alter their substantial risk in doing so,” the political scientists Wendy L. Hansen, Michael Rocca and Brittany Ortiz of the University of New Mexico, Albuquerque, argued in a recent study.

Still, corporations’ reluctance to open their checkbooks suggests an intriguing alternative explanation for the rise of Republicans who are willing to defy their will: companies may have spent too little. Their money was swamped by that of big individual donors who are more ideologically extreme. In 2012, the top 0.1 percent of donors contributed more than 44 percent of all campaign contributions. In 1980 their share of contributions was less than 10 percent.

Corporations have a pro-Republican bias, of course. But it is not quite as extreme as pop culture would have it, and is certainly less pronounced than organized labor’s pro-Democrat leanings.

Effective lobbying requires both Republican and Democratic friends. Political action committees run by businesses are known for spreading money on both sides of the partisan divide. They give to incumbents. They choose winners. They show little partisan loyalty.

In the 2006 elections, when the G.O.P. controlled Congress, corporate PACs gave 65 percent of their money to Republicans. In 2008 and 2010, after the Democrats had swept both the House and Senate, they split their contributions roughly fifty-fifty.