Bill Cohen, the former three-term Republican U.S. senator from Maine who served as secretary of defense in Democratic president Bill Clinton’s second administration, offered this key to the art of winning tough elections: “I don’t care how great your ideas are or how well you can articulate them. People must like you before they will vote for you.”

Nowhere is this “like” factor more important to the decision of voters than when they choose a president. Consider this: In the campaigns of 2000 and 2004, the Democratic nominees, Al Gore and John Kerry, were both seen by voters to be more knowledgeable and more intelligent than George W. Bush, the Republican. Yet Bush was seen, by those same voters, as more personally likable than Gore and Kerry, and Bush won. In the experienced judgment of Democratic pollster Peter D. Hart, “voters value ‘I like’ over IQ.”

Which brings us directly to the 2016 presidential campaign and the doomed candidacy of real estate billionaire Donald Trump. A quick check of the record reveals this representative sample of individuals Trump has publicly branded as “a loser”: former Florida Gov. Jeb Bush, Sen. John McCain, President Barack Obama, conservative columnist and Fox News analyst Charles Krauthammer, British Prime Minister David Cameron, and “Meet the Press” host Chuck Todd. According to Trump’s discriminating tastes, Sen. Lindsey Graham is “an idiot” and Hillary Clinton “was the worst secretary of state in the history of the United States,” while the 2012 GOP nominee is dismissed this way: “I have a Gucci store that’s worth more money than (Mitt) Romney.”

OK, Trump’s defenders concede, their candidate’s language can sometimes be insulting and offensive. But they make the case that Trump’s wounding rudeness is just proof of his refreshing candor. You can argue he’s blunt and unscripted, but you cannot believably argue that either he or what he regularly spews is likable.

Americans want their chief executive to be more than just the commander in chief. They also want their president to be, in time of crisis, the comforter in chief, as well as the teacher in chief and a leader in chief who understands when to stand firm and when to compromise in the national interest.

On the commander-in-chief test, recall what Trump recently said in Iowa about John McCain. He declared that McCain was “not a war hero. He’s a war hero because he was captured. I like people that weren’t captured, OK?” McCain was not a hero because he was captured in the Vietnam War. What made him a hero was how he conducted himself in captivity. In spite of sustaining permanently crippling injuries and enduring brutal torture, McCain, the son and grandson of Navy admirals, rejected his captors’ offers for early release, choosing to endure, for five years, that ordeal with his fellow prisoners in Hanoi.

Trump, like so many sons of privilege of his generation, made sure he was among the “people that weren’t captured” by avoiding the U.S. military draft, pleading a bone spur in his foot. While McCain was being brutalized by the North Vietnamese, Trump had his own challenges stateside, where he was able to join “the hottest club in” New York. “It was the sort of place where you were likely to see a wealthy seventy-five-year-old guy walk in with three blondes from Sweden,” he wrote. McCain probably had no idea what he missed by volunteering to serve his country.

People must like you before they will vote for you. Donald Trump is not a likable man.