Mitt Romney and Barack Obama clash on nearly every important issue, from taxes to abortion to regulation to climate change. Yet both men adore their families, and they make sure we know it, too.
Throughout his administration, Mr. Obama has made reference to his daughters when defending women's rights or describing a hopeful vision of the future, and the first endorsement that he received at the Democratic convention was, of course, from his wife, Michelle.
Mr. Romney, for his part, made sure to effusively praise his wife, Ann, during his own acceptance speech. "Unconditional love is a gift that Ann and I have tried to pass on to our sons and now to our grandchildren," Mr. Romney declared. "All the laws and legislation in the world will never heal this world like the loving hearts and arms of mothers and fathers."
Voters from both parties clearly expect, even demand, this kind of talk from aspirants to the White House and anyone who becomes the unofficial father of the nation. They implicitly embrace the idea that to be a successful president, a man must have a good marriage and close, harmonious relationships with his progeny.
But based on the historical record, the voters are quite mistaken. In fact, hardly any of our most consequential chief executives would have been able to live up to the current standard of presidential uxoriousness and fond paternity.
Think of the three icons whose miniature, exchangeable portraits you carry around in your wallet.
George Washington had no children of his own, and he placed devotion to his work over devotion to his wife; exasperated by all the official dinners she was forced to attend, Martha complained, "I am more like a state prisoner."
Andrew Jackson's wife Rachel died two weeks after he was elected in 1828; the couple had no offspring.
Abraham and Mary Todd Lincoln were content enough until they moved into the White House. But in 1862, the death from typhoid of their young son Willie hurtled both husband and wife into a serious depression. Mary took to visiting spiritualists in order to "talk" to Willie, berated Abe in public when she thought he was flirting with other women and went on costly shopping sprees in the middle of the Civil War.
And that's not to mention Thomas Jefferson, a widower whose most enduring sexual relationship was probably with one of his slaves.
This blemished tradition continued during the 20th century, even as the media increasingly hunted down details about the private lives of public men.
Woodrow Wilson's wife died midway through his first term, and many Americans disapproved when he remarried a much younger woman just 16 months later.
Franklin and Eleanor Roosevelt were excellent political partners, but they stopped sharing a bedroom long before he became president; if Eleanor had a sex life while serving as first lady, it was almost certainly with another woman.
We now know, of course, all about JFK's multiple liaisons, affairs and quickies in the White House pool.
Ronald and Nancy Reagan seem to have had a close and happy marriage. But he spent little time with his four children, and each one confessed he was distant and enigmatic.
Why then, despite the evidence that great presidents are not the product of private bliss, do both parties continue to affirm the mawkish ideal? Surely part of the reason is the enduring power of the romantic, evangelical notion that only morally resolute individuals can lead us to build a moral society. Christian doctrine may preach original sin, but modern believers (and nonbelievers) continue to hope their presidents will be paragons of domesticity.
But an even greater role is played by the enduring power of the cultural conflicts that began in the 1960s. First, the feminist movement transformed the personal into the political. As more women starting running for office and gaining influence in government, policies on such matters as early childhood education gained the spotlight, as did workplace issues like sexual harassment. Meanwhile, the habitual infidelity of certain male politicians quickly went from being a press-room secret to a firing offense.
The rise of the Christian right in the 1970s also played a role. Viewing feminism as a dire threat to all they held dear, this new religious movement defined the family as "the fundamental institution of society, an immutable structure established by our Creator" and persuaded both evangelical Protestants and traditionalist Catholics that abortion and gay rights were diabolic rejections of God's plan.
Add in the fear that fewer heterosexual nuclear families signals national decline, stoked by conservative intellectuals like Charles Murray and echoed by right-wing talk-show hosts, religious and secular. No wonder male candidates from across the political spectrum keep trotting out their wives to testify to their humility, kindness and splendid child-rearing skills -- and often hint that they are also pretty good in bed.
A president who is a faithful loving husband and an attentive father is certainly preferable to one who is neither. But since the men who saw the nation through the Civil War, both world wars and the Great Depression didn't fit this model, perhaps we shouldn't make it a central part of the job description today either.
Perhaps we will have to wait for the first unmarried president -- straight or gay, male or female -- to burst the sentimental bubble.
Michael Kazin is a professor of history at Georgetown University and co-editor of Dissent. His latest book is "American Dreamers: How the Left Changed a Nation." This article first appeared in The New Republic.