Above: Ronald Reagan and his presidential-campaign chairman, William Casey, in June 1980.

Ronald Reagan knew how to do it. So did Bill Clinton. Their secret? They ignored the conventional wisdom. Here is a brief excerpt from an article co-authored by Rich Karlgaard and Michael S. Malone for The Wall Street Journal. To read the complete article, check out others, and obtain subscription information, please click here.

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As the 2016 presidential candidates start the long downhill run to the primaries early next year, the real test of their campaign teams begins.

If history is any guide, many of today’s highflying contenders will fall to earth in the next nine months, dragged down by dysfunctional organizations. What is astounding is that for all their experience running gubernatorial, senatorial or corporate staffs, most of this year’s candidates will repeat the same mistakes that have sunk their predecessors for generations.

For example, Jeb Bush is assembling a team of “superstars,” some of the best names in the campaign business. Hillary Clinton has pulled together staff based primarily on their compatibility and loyalty to her. Both strategies are usually recipes for disappointment.

We have been studying how effective teams work. Much research has been done the past 15 years that can shed light on this question—by anthropologists, sociologists, brain scientists and even cultural historians, who have uncovered common organizational archetypes that have held through the ages. If we’ve learned anything, it is that conventional wisdom about building and leading successful teams is almost completely wrong.

Here are [the first two of five] common mistakes:

o The more, the merrier. Why not bring as much talent, experience and intellectual firepower to the challenge as you can afford? There is, in fact, a mathematical argument against doing precisely that. Every new node in a network adds many more potential connections. Thus, while a team of four has just six interconnections, a team of 16 has 120 interconnections. It is near-exponential growth: n * (n-1) / 2.

Hierarchies help, but every additional team member adds complexity that can slow down decision-making and hamstring adaptability—not good when elections are won or lost on quick responses to the other candidates’ claims. As psychologist J. Richard Hackman told the Harvard Business Review in 2009: “Big teams usually just wind up wasting everybody’s time.” Better to use the smallest possible team that can get the job done.

o Recruit for compatibility. That is a recipe for, at best, second-rate results. After Doris Kearns Goodwin published Team of Rivals, her 2005 book on the Lincoln administration, came a flurry of interest (especially at the Obama White House) in teaming up people who fought on opposite sides of political battles. The downside is that rivals may not be able to fully put aside their differences.

Instead, the best solution is a team whose members complement one another. In other words, recruit for maximum diversity. A team with members of different viewpoints is not only less likely to err because of groupthink, but also more likely to come up with novel solutions to problems, according to research by Scott Page, a professor at the University of Michigan.

This doesn’t mean finding people of different races who all went to the Kennedy School of Government, but rather individuals with different life experiences, talents, cognitive skills and personalities. Bill Clinton’s 1992 “War Room” — with its crazy quilt of personalities such as James Carville, George Stephanopoulos and Paul Begala — is the defining example. Consider the difference between Mr. Obama’s 2008 hugely successful campaign team—a diverse mix of Silicon Valley whiz kids, Chicago pols and party veterans—and his underperforming administrative team.

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Here is a direct link to the complete article.

Mr. Karlgaard, the publisher of Forbes, and Mr. Malone, a technology journalist, are the authors of Team Genius: The New Science of High-Performing Organizations, recently published by HarperBusiness.