Donald Trump is acting like a clown, so the press has to cover a circus. (AP Photo/Rainier Ehrhardt)

The notion that the media could control a presidential campaign was always bogus. News organizations enjoy the ratings and readership delivered by Donald Trump — just ask CBS boss Les Moonves — but they haven’t made him the Republican presidential front-runner. Voters who ignore or even embrace his venomous brand of politics and the many negative stories about him have done that.

If it were up to the press, John Kasich would be the GOP nominee.

But whatever control the media did have feels lost after a week that began with a distasteful, super PAC-sponsored ad campaign featuring a mostly nude Melania Trump and ended with a tabloid rumor about extramarital affairs by Sen. Ted Cruz (R-Tex.).

In between, Donald Trump cryptically threatened to “spill the beans” about Cruz’s wife, Heidi, then retweeted a set of photographs meant to insult Heidi Cruz’s physical appearance.

As of Wednesday morning, I still thought the press could keep this circus in one ring. That was after the “spill the beans” tweet, and I figured journalists would have to acknowledge it in their reporting but could prevent a juvenile episode from becoming a big deal — by not making a big deal out of it.

How wrong I was. Trump retweeted the photos late that night, and Heidi Cruz felt compelled to address them on Thursday. Gotta cover that, after all.

Meanwhile, on Wednesday afternoon, the National Enquirer had published a gossip piece alleging affairs by Ted Cruz. Virtually every news outlet with a conscience ignored it. Then a Trump-loving radio host making a guest appearance on CNN on Friday brought it up on live television — and suggested that former Cruz communications director Amanda Carpenter, who was also on the air across the screen, had slept with her onetime boss.

Carpenter denied the charge, Cruz concluded that he had to do the same, and suddenly this thing that the media had tried to avoid was a major story.

Out. Of. Con-trol.

It’s convenient to blame the media for Trump’s rise, but the reality — made dishearteningly apparent this week — is that the press isn’t powerful enough to be responsible for his success or failure. It can’t even control the campaign narrative, never mind the outcome.

Washington Post columnist Eugene Robinson explained the fallacy of media scapegoating perfectly on MSNBC’s “Morning Joe” last month.

I hear from a lot of voters and a lot of interested people, and there’s almost a form letter, a template for the most common criticism I get, which is: “Why doesn’t the media hold Politician X accountable for Y?” Right? And I write back: “What do you mean? Because we ask the politician about this, we ask follow-up questions, we point out that what X said or Y said was a lie. What you’re objecting to is the fact that the politician you don’t like — that his or her campaign didn’t immediately collapse.” And that’s what people react to.

Robinson is exactly right. The media can’t just decide to get tougher on Trump, or to ignore Trump, and bring an end to his White House ambitions. And if he turns the election into a three-ring circus, then reporters have to cover a three-ring circus. They can point out how tawdry his act is — how unpresidential it is — but it’s up to voters to walk away from him.

There are many words to describe the week, but for the media, “humbling” is probably the most apt. Journalists might take some small comfort in knowing they didn't actually create the Rise of Trump, but they’re likely even more dismayed that they seem to wield so little influence over how, and whether, they cover the clownish antics of his big-top campaign.