Editor's Note: (Julian Zelizer is a professor of history and public affairs at Princeton University and a New America fellow. He is the author of "Jimmy Carter" and "The Fierce Urgency of Now: Lyndon Johnson, Congress, and the Battle for the Great Society." The opinions expressed in this commentary are his.")
(CNN) Donald Trump really turned some heads on Sunday when he said that the Russians were not going into the Ukraine.
"He's not going into Ukraine, OK, just so you understand. He's not going to go into Ukraine, all right? You can mark it down. You can put it down. You can take it anywhere you want," he told George Stephanopoulos on ABC's "This Week." When the host pointed out to Trump that Putin was already in the Ukraine, Trump responded, "Ok, well, he's there in a certain way." Regarding Crimea, a part of the Ukraine which Russia has occupied, he said: "the people of Crimea, from what I've heard, would rather be with Russia than where they were."
For anyone who followed the aggressive moves by the Russians in Crimea and eastern Ukraine, these comments were pretty hard to believe.
Besides renewing the ongoing questions about campaign adviser Paul Manafort's interests in the Ukraine, the statements raised even more concern about how much of a grasp Trump really has on key public policy issues --about which he speaks frequently -- and how much he cares to learn.
There have been a number of profiles in the press that indicate Trump doesn't have the greatest attention span in the world and he is not someone who is very determined to learn about the issues.
Many foreign policy experts are deeply concerned that Trump, who admittedly doesn't like to read books, is willing to make big and bold statements about foreign policy without actually knowing what he's talking about. Foreign policy expert Max Boot, a senior fellow at the Council on Foreign Relations who advised three Republican presidential candidates, blasted the GOP in The New York Times by saying, "It's hard to know exactly when the Republican Party assumed the mantle of the 'stupid party.'"
Of course, some Trump supporters will point out that "gaffes" are a regular part of presidential campaigns and don't necessarily tell us how a person will perform in the White House.
One of the most famous missteps on foreign policy took place nearly 40 years ago, during a televised debate in October 1976 between Republican President Gerald Ford and Democrat Jimmy Carter. Ford had been under fire from right wing Republicans such as Ronald Reagan (who challenged him in the primaries, and almost won) for his policy of detente with the Soviet Union.
Working with Secretary of State Henry Kissinger, Ford had undertaken a series of steps, like his predecessor Richard Nixon, to ease tensions with the Soviets. His critics charged that Ford had turned a blind eye toward the oppressive conditions under which Eastern Europeans were forced to live.
Before the debate, Ford had prepped to give a strong and compelling answer to these attacks. When one of the moderators asked him if detente meant that the administration had accepted the status quo, Ford answered that there was "no Soviet domination of Eastern Europe, and there never will be under a Ford administration."
Viewers stared into their television screens and couldn't believe what they just heard. When Max Frankel followed up by asking: "I'm sorry, what?" continuing, "Did I understand you to say, sir, that the Russians are not using Eastern Europe as their own sphere of influence in occupying most of the countries there and making sure with their troops that it's a communist zone?" Ford did not change his answer.
When his advisers urged him to apologize for the statements after the election he refused to do so. Many observers believed that the response cost him the election.
In that infamous moment, the problem was not that Ford, who not only was the sitting president but had served as House minority leader for several years, actually thought the Polish, Romanians and Yugoslavians had somehow freed themselves from Soviet domination. What he wanted to indicate was that the people living in those countries did not accept the legitimacy of Soviet authority, and neither did he. The words came out wrong and he didn't fully grasp the impression that his statement conveyed.
There is a big difference between moments like these and the many instances where Trump has displayed a fundamental lack of knowledge about events taking place in parts of the world where he has expressed strong opinions about what's right and what's wrong (in addition to the fact that Ford was opposing Soviet domination, whereas Trump at times seems fine with the Russians asserting control over sovereign countries).
Although Trump supporters like to point to Brexit as evidence that his campaign is part of an international revolt against elites who have failed workers and been too liberal with immigrants, he didn't recognize the term when asked shortly before the vote occurred.
He's made a number of other significant mistakes over the past year, such as confusing Iran's Revolutionary Guard Quds forces with the Kurds.
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Voters can't afford to ignore this recurring problem and Trump must be pressed to demonstrate that he does have a strong grasp of the major issues the nation faces and, just as important, that he is devoting time and energy to learning everything he needs to know.
Although it is true that most presidents surround themselves with smart and knowledgeable advisers, presidents themselves must ultimately make the decisions when the experts disagree, as Max Boot pointed out, and must be able to tell when experts are giving them bad advice.
It is one thing to slip up on the campaign trail, it is another to be going around making pointed and controversial claims without actually knowing about the key events that have been taking place.
The question is: where are American voters today? This is the big unknown. When Sarah Palin revealed stunning weaknesses in her policy expertise during a series of interviews with Katie Couric shortly after her nomination, it hurt her and GOP presidential nominee John McCain.
But what many experts wonder today is whether there are large parts of the electorate who just no longer care, whether anti-intellectualism and a disdain for expertise has created an electoral climate where it is accepted as legitimate to make pointed arguments about other countries without really knowing much about the facts on the ground.
That's what we'll learn in November.