“I think it’s a function of the unique nature of this election, in which you have really high-caliber candidates who are essentially identical on the issues,” Robert F. Kennedy Jr., who has thrown in his lot with Mrs. Clinton, said in an interview.  In any election, members of the same families choose competing candidates. But while some primaries hinge on policy differences, this one also turns on the deep, perennial disagreements between parents and children, husbands and wives. Older family members argue with younger ones about experience versus freshness. Men and women question whether they operate on a level playing field. And when husbands and wives discuss the Clinton marriage, they often touch on raw issues within their own.  Take the Sanchez sisters, whose dispute has the contours of a classic big sister-little sister fight. It started with a pact: Though both are California Democrats, neither would endorse a presidential primary candidate.  But last month, after listening to her older sister praise Mrs. Clinton to a colleague, Linda T. Sanchez, 39, realized that she fervently disagreed. Swept up in excitement, she endorsed Mr. Obama — without calling her sister, who found out through aides. Hours later, Loretta Sanchez, 48, issued her own opposing endorsement. For weeks afterward the two spoke together only in joint interviews.  Loretta Sanchez, who has been in Congress for 12 years, twice as long as her sister, scoffed at what she implied was her sister’s immaturity and lack of gratitude. “Her one comment was, ‘He reminds me of John F. Kennedy.’ I was like, You weren’t even born when he died!” she said, laughing. “She was tilting at windmills, with stars in her eyes and her feet off the ground.”  “My sister benefited from so many things the Clintons did,” Loretta Sanchez continued, mentioning student loan legislation. Obama supporters “don’t understand what it took to get all those things done.”  In an interview of her own, Linda Sanchez defended her choice — and her youth. “I know the frustration of being young, of being someone who has ideas outside the box and has difficulty making change in Washington,” she said. Sometimes, her efforts are rejected “because I’m seen as too young or naïve, and I hate that,” she said.  And her sister’s recent assertions on television that the rest of the family is voting for Mrs. Clinton are wrong, she claimed.  “They don’t want to tell her,” Loretta Sanchez countered.  Things are more peaceful in the Denver household of Heidi Wald and Philip Weiser, who teach medicine and law, respectively, at the University of Colorado. She is for Mrs. Clinton, he is for Mr. Obama, and they have remained congenial about it — even when Mr. Weiser held a party for Obama supporters at their home last week.  “All my girlfriends were like, How did you let him do that?” Ms. Wald said.  “I have a newborn so I can’t organize events myself right now,” she added.  Indeed, the race is playing out at a moment when, despite their equally impressive educations and jobs, the birth of a new child has landed the couple in very different roles. (Mr. Weiser conducted his interview while striding through an airport on his way to a conference, but when Ms. Wald first picked up her telephone, she needed to break off to change their squalling infant’s diaper.)  So the race, Mr. Weiser said, has become a mirror in which the couple sees bits of themselves. While male candidates like Mr. Obama have spent long periods away from their young children, the same might not be tolerated from a female candidate. “Could Michelle Obama run for president with kids like that?” Mr. Weiser asked dubiously.  Other members of divided Democratic families are starting to mimic the behavior of the candidates they support, treating their relatives more like competitors. Susie Tompkins Buell, a fund-raiser for Mrs. Clinton in San Francisco, is politely avoiding her stepson, Justin Buell, who is gathering donations for Mr. Obama, and vice versa. (The two have solicited some of the same donors.) Since the start of the primary season, they have communicated only through the terse congratulations the loser delivers after each primary or caucus.  Christopher Edley and Maria Echaveste, a married couple who met while serving in the Clinton administration, have actually started debating each other. Not just at their kitchen table, but in front of audiences across California and on television.  “It’s not easy,” Ms. Echaveste, who is a paid consultant to Mrs. Clinton, said in a joint telephone interview with her husband, who advises Mr. Obama. “You’re having a discussion and your husband is basically saying that your candidate doesn’t have a moral compass.”  With that, Mr. Edley broke in. “Or your wife is saying that your candidate isn’t smart enough to figure out where the bathrooms are,” he said.  “I never said that,” she replied.  The couple has relived some of the campaign’s most rancorous moments, such as when Ms. Echaveste, echoing Bill Clinton, told her husband that Mr. Obama was “naïve.” The word conjured up racial stereotypes for Mr. Edley, who is black, and has known Mr. Obama since he taught him in law school. “There’s the childlike Negro,” he explained. “There is the superficial but glib minstrel.”  Ms. Echaveste, who is Hispanic, now understands why her husband exploded in response. “Regardless of being dean of a law school” — at the University of California, Berkeley, where both teach — “he’s still in a box called being a black man,” she said. Still, she said, “I ought to be able to make that point and not trigger these reactions.”  And with that, Mr. Edley responded, his wife countered, and they started to debate once more.  A version of this article appears in print on , on page A1 of the New York edition with the headline: In Democratic Families, Politics Makes for Estranged Bedfellows. 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Political dynasties and ordinary people alike have found their houses divided between support for Hillary Rodham Clinton and Barack Obama.