Regular readers may recall my reticence about candidate debates as revelatory moments. As I’ve written before, the skills honored in debate performances are not necessarily those demanded by the presidency.  Nevertheless, debates can sometimes help illuminate or highlight a candidate’s thought processes.   That’s especially true for a proudly unpracticed and unrehearsed candidate like Donald Trump.  For example, that Trump is a serial liar is not news.   Washington Post fact-checkers counted 30,573 false or misleading claims by Trump during his White House tenure—a staggering average of over 20 each day of his presidency.   The debate was replete with Trump lies as well—30 by CNN’s preliminary count.   But what struck me during the debate was not just the number and frequency of the lies but that Trump’s first reaction to the slightest pressure seems to be to lie.  Trump could have reacted in several ways when Vice President Harris noted that the Wharton Budget Model found his economic plan would “explode the deficit.”   He could have ignored the attack and repeated the alleged virtues of his plan, or in MAGA style, ridiculed ivory tower academic economists, or attacked Harris’s plan, or focused on the inflation voters have felt under Biden-Harris or taken several other paths.  What was his first reaction? To lie.  “…I went to the Wharton School of Finance and many of those professors, the top professors, think my plan is a brilliant plan…”  In fact, not one Wharton professor seems to have endorsed his plan, let alone graded it “brilliant.”   Challenged in any way, Trump’s first reaction is not to survey the facts and knit them into a compelling argument. Rather it is simply to make-up a bald-faced lie.   That’s not a desirable character trait in a six-year-old or in a president.   Trump is also frighteningly gullible, seemingly unable to distinguish trustworthy sources of information from highly questionable ones.    Trump accepted Sen. JD Vance’s (R-Ohio) story about Haitian immigrants in Springfield, Ohio, eating pets because, “I've seen people on television.”  That the Republican mayor, the Republican governor, the city manager and the police chief all maintain the allegations have no merit means nothing to Trump because, “I've seen people on television.”  The fact that the lies he’s spewing are causing tremendous harm to Springfield’s residents is- seemingly irrelevant for Trump because, “I've seen people on television.”  While president, on a wholly separate occasion, Trump was asked whether he believed America’s intelligence community or Russian President Vladmir Putin when it came to questions about Russian attempts to influence the U.S. election.   Trump’s privileged source? Putin. Now, believing the intelligence community on every matter would be unwise, but choosing Putin as a more reliable source is nuts.   As the debate evidenced, though, it reflects a pattern of dangerous gullibility.  Also terrifying is Trump’s apparent inability to understand basic processes.   Consider the basis of Trump’s conclusion that he must have won the last election, “…there's so much proof… I got almost 75 million votes. The most votes any sitting president has ever gotten. I was told if I got 63 [million], which was what I got in 2016, you can't be beaten.”  As every fifth grader knows, that’s not how our system works. Trump seems to believe that some apparatchik sets a level of vote before the election and if you get that number of votes you win.   He doesn’t seem to realize that the winner is the candidate who gets at least 270 electoral votes and that the number of votes one needs to win a state depends on turnout. The more people who vote, the more votes one needs to win.   The voting eligible population has increased every four years at least since 1980, though the level of turnout of that population varies.   In 2020, about two-thirds of eligible voters cast a ballot. That left almost 80 million people legally eligible to cast a ballot who chose not to—enough for either candidate to have gotten many millions more.  Trump’s expressed misunderstanding of the basic electoral system in which he has participated three times ought to be shocking.   Never before has a major party put forward a candidate for president with as many serious psychological and intellectual impairments as Donald Trump.  I only hope folks notice before Election Day.   Mark Mellman is a pollster and president of The Mellman Group, a political consultancy. He is also president of Democratic Majority for Israel.