In rhetorical study, we know that presidential campaigns are essentially persuasion campaigns that comprise agenda — the issues discussed — and spin, essentially the way they're discussed.

In 1960, the question of what to do if “Red China” — as it was called then — imperiled the islands of Quemoy and Matsu became the focal point of a major debate and campaign dispute between John F. Kennedy and Richard M. Nixon in their close election. Kennedy made Quemoy and Matsu into a representative issue that illustrated how he and Vice President Nixon differed in their dependability in handling nuclear weapons policy. And he won the election.

That was the first agenda struggle in the modern presidential campaign era, but it would be the kind of competition that clearly is important in all elections and was decisively important in 2008 and 2012 — and maybe in 2016, as well.

The failed campaigns of John McCain and Mitt Romney in 2008 and 2012 respectively can be attributed to their lack of control of agenda and spin, especially agenda, and the contrary effort by much of the media to discuss issues that are secondary. To his detriment, Mr. McCain largely ignored associations of Sen. Barack Obama that could have devastated the senator's campaign, such as his interactions with radical leftist Bill Ayers, felon Tony Rezko and the anti-Semitic, anti-American Rev. Jeremiah Wright. The media, unsurprisingly, did not focus on them either.

Unlike Mr. McCain, Gov. Mitt Romney's campaign wasn't undone by what he left unsaid, but by what he said, specifically his claim that “there are 47 percent of the people who will vote for the president no matter what.” They are people, he continued, “who are dependent upon government, who believe that they are victims, who believe the government has a responsibility to care for them, who believe that they are entitled to health care, to food, to housing, to you-name-it. That that's an entitlement. And the government should give it to them. And they will vote for this president no matter what.”

Chuck Todd of NBC in particular along with other major progressive media sources played “gotcha” with this statement, and turned it into a permanently salient issue in the campaign, minimizing focus on the then-struggling economy and the president's foreign policy.

In 2016, Donald Trump also faces a hostile media, but unlike Mr, Romney, he is more than complicit in the negative coverage: He helps to minimize attention paid to issues that benefit him and to maximize issues that detract from his popular and electoral support.

The consistent criticism from those who don't want Hillary Clinton to win the presidential election has been that Donald Trump won't stay on message; he highlights irrelevant, often out-of-date personal issues in place of issues that raise opposition toward Ms. Clinton. Megyn Kelly of “The Kelly File” expressed her bewilderment over this earlier in the month, asking “What is he doing relitigating every controversy from the primary season?” And in response, Benjamin Domenech, the publisher of The Federalist noted that “it is like this every day.”

No significant supporter of Mr. Trump has even attempted to publicly articulate a compelling reason for the presidential candidate's attacks on the parents of the heroic Capt. Humayun Khan, who was killed in action in Operation Iraqi Freedom, sacrificing himself to a suicide bomber and likely saving the lives of hundreds of soldiers nearby. It is an American commonplace that such Gold Star parents are to be left uncriticized — and particularly left uncriticized repeatedly.

Such rhetorical problems make Mr. Trump's agenda perfect for Hillary to maximize her Democratic and centrist Republican support. His campaign is doomed without a change in course, though it may already be too late for even that. An attempt to capitalize on Hillary Clinton's recent slip of the tongue, saying she “may have short-circuited” the truth regarding the FBI's investigation of her emails, became not an indictment of her trustworthiness, but a means to question her sanity — an issue that has been repeatedly raised about Mr. Trump himself.

Perhaps Mr. Trump was hoping to deflect his own mental fitness scrutiny, aware of what befell Mitt Romney's father. In the 1968 presidential contest, George Romney rhetorically self-destructed when he explained that his early opinion supporting the Vietnam War was due to American generals' having “brainwashed” him. The media jumped all over him, and his candidacy never recovered.

As has been pointed out, Ms. Clinton said she had short-circuited her answer, not that she herself “short circuited.” Again, by making the issue personal rather than focusing on her deceptions, Mr. Trump avoids making her untruths an agenda issue.

If he continues to allow minor personal matters and petty grievances against Hillary and irrelevant others to become dominant issues, and to ignore the issues that will devastate his opponent, his election agenda will preclude victory.

Richard Vatz has taught political persuasion at Towson University for four decades and is the author of The Only Authentic Book of Persuasion: the Agenda-Spin Model (Kendall Hunt, 2013). His email is rvatz@towson.edu.