WASHINGTON — Regular readers of this space may recall that I believe Americans are the most optimistic of voters. Think about it: With the exception of those who were already here when Christopher Columbus arrived and those who were brought here against their will in chains, every American is either an immigrant or the direct lineal descendant of immigrants. Much has been written, even rhapsodized, of the courage required to immigrate: to leave behind family and friends, to strike out across the sea or the continent, to live among people you have never known and to learn a language you have never heard.

But to be an immigrant is also a profound statement of optimism: Here we are, free to make our lives and the lives of those whom we love fairer, fuller and better. That same optimism has shaped Americans’ presidential vote. When a president disappoints us, we almost immediately go looking for the next presidential candidate with the qualities that were missing in his predecessor who just let us down.

For example, Richard Nixon was arguably the most experienced White House nominee ever elected. His credentials included service in the U.S. House and the U.S. Senate, followed by eight years as Dwight Eisenhower’s vice president. But the criminality of Watergate and Nixon’s resignation in disgrace gave experience a bad name. In the next election, Jimmy Carter, a former one-term Georgia governor, could make the case to American voters that his lack of Washington experience was a plus and, somehow, evidence of his personal integrity.

President George H.W. Bush ran into rough economic seas when running for reelection, and when Bush appeared unfamiliar, even confounded, by the electronic price scanner at a supermarket checkout, voters wondered if he understood the hard times they were enduring. His Democratic challenger told them, “I feel your pain,” and the electorate found the empathy in Bill Clinton they were seeking in their next president.

Every president for the next 24 years, beginning with Clinton, was reelected to a second White House term because they, compared with their challengers, possessed the qualities voters prized in their chief executive.

For example, when Clinton won reelection, about half of voters, according to the Gallup poll, believed he “shared their values”; 63% said he “cares about the needs of people like you”; and a majority said he “puts the country’s interests ahead of his own political interests.” George W. Bush, seeking reelection, also won positive grades in the Gallup poll: a solid majority judged him “honest and trustworthy”; 72% said Bush had “strong moral character”; and healthy majorities found him a “person you admire” and someone who had “brought dignity back to the White House.” Barack Obama, winning reelection, was judged “honest and trustworthy” by 60% of voters and “likable” by 76% of voters, with 58% believing he “understands problems Americans face in their daily lives.”

Donald Trump became the first U.S. president in the 21st century not to win reelection. Why? First, 62% of voters judged Trump to be not “honest and trustworthy”; 63% rated him not “likable”; and only 35% of voters called him “a person you admire.”

In Joe Biden, American voters saw the empathy, trustworthiness, experience and likability that were lacking in the Republican incumbent. Not for the first time, optimistic Americans went looking for — and finding — those very qualities missing in the president who had most recently disappointed them.

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To find out more about Mark Shields and read his past columns, visit the Creators Syndicate webpage at www.creators.com.