Remember all that scary rhetoric about 'Citizens United'? What we've learned from this election cycle

Even during the presidential primaries it was obvious that traditional TV advertising wasn't working as well as it once did: Four Republican candidates were outspending Donald Trump but losing to him, and Bernie Sanders spent more on TV spots than Hillary Clinton. Now, with the general election campaign in full swing, the efficiency of TV ads remains in doubt.

The poll results from hotly contested states published since Sept. 15 show Donald Trump and Hillary Clinton within one to eight percentage points of each other; each candidate is leading in some of the battlegrounds. Libertarian candidate Gary Johnson is a distant third with varying levels of support -- 4 percent in Ohio and 14 percent in Pennsylvania.

Using spending data from Kantar Media's Campaign Media Analysis Group, I added up up the candidates' estimated TV ad expenditures between July 1 and Sept. 15 in nine contested states. I added in shares of national TV ad spending, weighting them by the states' population. On average, one percentage point in polls cost Clinton almost $214,000 during that period. Trump paid an average of about $60,000 per percentage point, and Johnson a mere $4,000.

Clinton is running her TV advertising the old-fashioned way, as a multinational corporation would for an important product. She doesn't just far outspend her rivals -- her ad expenditure in contested states is rather highly correlated with her poll ratings in those areas. This means Clinton's ads actually work, and she can improve her standing where she needs to by spending more.

In the last 30 days, according to CMAG, Clinton spent the most -- about $6.3 million -- running an ad in which veterans, some of them disabled, are shown watching incredulously as Trump compares his personal sacrifice to theirs and questions the heroism of Senator John McCain. Most of the Clinton money pays for attack ads of this kind. They are far better and more emotionally engaging than the political commercials I saw while covering the primaries: Obviously, more creative effort went into them.

By comparison, Trump's ad campaign is haphazard. The spending is uncorrelated with the Republican nominee's poll ratings in the contested states. He has put a lot of eggs in one basket, spending more than $10 million on an ad that I found unconvincing. It shows an America under Clinton that is all locked factory gates and disappointed faces. Trump's America is smiling workers and happy families. It's primitive and unsubtle, and is unlikely to sway anyone who isn't already a supporter. The candidate and Republican PACs are spending far less money attacking Clinton's specific weaknesses.

Yet Trump leads in the polls in six of the nine states I analyzed.

In part, this is due to his heavy use of digital advertising and the emergence of his ground operations. Still, Clinton is no less active on the internet and much stronger on the ground.

A number of candidates in this election have claimed that theirs are not campaigns but movements. Most of them have fallen by the wayside. Trump, however, is still standing, despite a weak advertising strategy. The forces at work have little to do with TV commercials and traditional campaigning. Trump has been raising and spending more money lately, but the sums pale compared to the outlays of the Clinton operation.

Johnson's performance is more evidence that U.S. presidential elections are not really outlay contests -- contradicting the likes of President Vladimir Putin, who recently said a candidate needed "several billion dollars" to compete for the White House, but also those who argued that money would overwhelm the system after the Supreme Court's Citizens United decision. The Libertarian candidate has spent almost nothing compared to the two main contenders and yet his poll ratings in states such as Pennsylvania and Colorado exceed 10 percent. Johnson's luck, of course, is that Clinton and Trump are so unpopular that any third-party candidate would be able to gain some traction.

None of this is to say that advertising has grown totally useless in U.S. politics. It may have been more effective in a less bitterly divided field and if the top candidates had higher positive ratings. This year, when one of the campaigns is a movement whose leader gets loads of free publicity, and when a third-party candidate looks unusually attractive thanks to the failings of the two major ones, ad spending is no less costly but far less helpful. This may well augur a permanent change to the way U.S. presidential campaigns are run: Other people with Trump's penchant for publicity are likely to be tempted to try his populist, cost-effective path. And perhaps a stronger third party will emerge.

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Leonid Bershidsky, a Bloomberg View contributor, is a Berlin-based writer.