The most disturbing trend in the financing of American political campaigns is not the magnitude of the money being spent. It’s that more and more of that money is not going through the campaigns themselves — where donations must be disclosed and limited — but from nonprofit groups that are being set up for the express purpose of frustrating any attempt to identify their funders.

This infusion of “dark money” all but obliterates the post-Watergate notion that Americans have a right to know who is behind the deluge of television ads, robocalls and mailers for and against candidates.

The Center for Responsive Politics, a diligent tracker of campaign finance, produced a fascinating analysis of the 2014 election. Its upshot: The amount of money spent in this midterm was only slightly larger than in 2010: $3.67 billion, compared with $3.63 billion in 2010.

The congressional campaigns themselves spent less than they did four years ago. However, the amount spent by outside groups grew 66 percent to $480 million, or 13 percent of the cycle’s overall spending, according to CRP.

Why should this concern us?

First and foremost, recent history has shown that the electorate can be highly skeptical of blatant attempts to buy elections. We saw that in Richmond, where voters defeated all four members of the Chevron-backed slate. We saw that in Berkeley and San Francisco, where solid majorities supported soda taxes that were fiercely opposed by the industry. Even though San Francisco’s Proposition E failed to meet the two-thirds threshold for passage, Coca-Cola and Pepsi cannot be comforted by the 54 percent who supported it.

The U.S. Supreme Court’s 2010 Citizens United Decision lifted the limits on so-called independent efforts as basically a matter of free speech: Individuals, corporations, labor unions and other advocates have a right to express their views.

But even the very concept of “independent expenditures” is being tested in this post-Citizens United environment. In North Carolina, the campaign of Republican U.S. Senate candidate Thom Tillis e-mailed a detailed strategy memo to supporters with a wish list of spending plans for the Asheville and Charlotte markets. Tillis eked out a victory over Democrat Kay Hagan in what became the nation’s most expensive race — with outside groups accounting for $81 million of the $113 million spent.

Also, in this new world order, various players are operating under different sets of rules — and some seem to be creating their own, aware that this Supreme Court seems disinclined to stop them.

We know, for example, that billionaire investor Tom Steyer spent $74 million on behalf of Democratic candidates who were committed to doing something about climate change. There is no exact figure on how much was spent at the other end of the spectrum by the Koch brothers, the conservative oil barons who funnel much of their donations through nonprofits that are not required to list their funding sources under the tax code. A memo by the Koch brothers’ main political arm, leaked to Politico in May, forecast a budget of $125 million in this election.

Such obfuscation is becoming more commonplace. Republican Sen. Mitch McConnell’s re-election had the assist of a secretly funded group called the Kentucky Opportunity Coalition. Its 12,000 TV ads accounted for one 1 out of every 7 in the race, according to the Center for Public Integrity.

So the average voter is left without knowing who really is behind these campaigns. But make no mistake: Our elected officials are well aware of their benefactors and their expectations.

John Diaz is The San Francisco

Chronicle’s editorial page editor.

E-mail: [email protected]

Money talked, but did not always prevail

$3 million: LOST

Chevron spent more than $3 million on behalf of four candidates for the Richmond City Council who were considered more friendly to the oil giant and its local refinery. All four were defeated.

Footnote: The election gave a huge lift to the East Bay city’s progressive movement.

$60 million: WON

Insurance companies and doctors spent heavily against Proposition 46, a measure backed by trial lawyers and consumer groups to lift the cap on “pain and suffering” in medical malpractice cases from $250,000 — the amount set in 1975 — to $1.1. million. It also would have initiated drug testing of doctors and required them to check a state database before prescribing certain drugs. It was rejected by more than two-thirds of California voters.

Footnote: This was easily the most expensive campaign in the state.

$11.5 million: SPLIT DECISION

The soda industry spent an estimated $11.5 million against proposed soda taxes in San Francisco (Prop. E, 2 cents an ounce) and Berkeley (Measure D, penny an ounce). Berkeley voters overwhelmingly approved Measure D, while the 54-percent “yes” vote in San Francisco fell short of the required two-thirds majority.

Footnote: Is the nation’s first soda tax the start of a national trend?

$25 million: WON

The election cycle began with Democrats thinking they could take out Senate Minority Leader Mitch McConnell, R-Ky. No such luck. His campaign outspent challenger Alison Grimes by $10 million, not to mention the boost he received from the many millions spent on his behalf by “independent” groups not bound by contribution limits.

Footnote: McConnell is about to become majority leader of the U.S. Senate.

$7 million: SPLIT DECISION

Local and national oil companies spent more than $7 million on campaigns against proposed fracking bans in Santa Barbara, Mendocino and San Benito counties. Santa Barbara voters rejected the ban on fracking and new permits for cyclic steam injection, a method for pulling oil out of aging fields. The measures passed in San Benito and Mendocino, though legal challenges are expected.

Footnote: Fifty-nine percent of voters in Denton, Texas, heart of the Barnett Shale Basin, passed that state’s first fracking ban.