When Mamie Eisenhower was first lady, expectations for political wives were simple: Smile for the family portrait, flanked by children, husband and pets.

A half-century later, the wives of presidential candidates are part of the political apparatus, for better or worse. Their involvement in the campaign is obligatory, even if they are lukewarm to it. The job description now: chief character witness, with personal past as fodder.

That, however, could be a challenge for two Republican hopefuls with messy marital histories.

Indiana Gov. Mitch Daniels, who is weighing a run, and his wife, Cheri, divorced in the early 1990s after she left him and their four children, ages 8 to 14. She married another man before divorcing again and remarrying Daniels a few years later.

Former House speaker Newt Gingrich, who announced his candidacy last week, is married to his third wife, Callista, whom he started dating while still married to his second wife.

Cheri Daniels and Callista Gingrich are said to be reluctant to step into the pressure cooker of a presidential campaign — which could force them to discuss the past publicly.

Even at this early stage of the campaign, shaping the narrative of home life is part of the political calculation, said Nicolle Wallace, who served as a senior adviser to John McCain’s presidential campaign and was an aide to President George W. Bush.

“The voters can tolerate messy and complicated, but they have very little patience for being lied to,” Wallace said. “They are not looking for June Cleaver.”

Polls show that, indeed, the public cares about a candidate’s family life.

Roughly half of voters said a candidate’s spouse would have some impact on their vote, according to a Washington Post-ABC News poll just before the start of the 2008 presidential primaries. Voters are much more interested in the candidate’s personal qualities and positions on issues. But for one quarter of voters, the spouse carries significant weight, the poll showed.

“People want to like the spouse. They’ll have an attitude” about that person, said Ruth B. Mandel, director of the Eagleton Institute of Politics at Rutgers University and a specialist in U.S. women’s political history. “If they don’t like the spouse, that will color how they feel about the candidate.”

What is important to Mary Frieden, president of the Muscatine County Republican Women in Iowa, is whether a candidate has support at home. “I like to see the spouse visible and supportive, holding the same values as the candidate,” she said. “It matters to me in the sense of good, sound family values. Seeing a good family that is tight and cares for each other means a lot to me.”

The politicians eyeing 2012 are no doubt pondering how to turn their marital histories into a silver lining in the storm narrative. The often-quoted response from Mitch Daniels, who routinely declines to speak publicly about his marriage, came in a 2004 article in the Indianapolis Star: “If you like happy endings, you’ll love our story,” he said.

Gingrich says that Callista helped him become a better man, and that it was her faith that led him to convert to Catholicism.

When Hillary Rodham Clinton was helping her husband run for president in 1992, questions about their marriage were a new, and uncomfortable, part of the public conversation. But such questions have become the norm. With so many political families forged by second — or even third — marriages, many political wives must now endure relentless scrutiny of their early days of courtship.

And in the 24-hour news cycle, spouses are a key part of the political story, with reporters and news cameras following them to events — just as they do candidates.

“There is absolute transparency of everything that you do. There’s always a telephone with a camera on it. You’re never off,” said longtime political spouse Debbie Dingell, whose husband, Rep. John D. Dingell (D-Mich.), has served in Congress since 1955.

Opting out of politics altogether was not a choice that appealed to her, she said.

By contrast, Judith Steinberg Dean, a physician and wife of 2004 Democratic presidential candidate Howard Dean, declined to campaign — a move that was derided by political pundits.

Reluctant political wives are not new political animals, but today’s intensified scrutiny and unyielding pace are putting even more pressure on them.

Before Mississippi Gov. Haley Barbour announced his decision not to seek the 2012 Republican presidential nomination, his wife told a Mississippi television station that the idea of a national campaign “horrifies” her.

As first lady of Indiana, Cheri Daniels has shunned traditional politicking, with her husband saying she is “anti-political.”

“There is no rule book for this as far as I’m concerned,” she recently told reporters, referring to her role as a political spouse.

She and her husband, who is being strongly encouraged to run by some Republicans, have carefully guarded the most sensitive part of their marital history.

Their story may not neatly fit ideas about the prototypical first family. But as time has shown, there is room for change, Mandel said. Someday, a man could be the first spouse.

“It isn’t simply a smiling housewife,” she said. “There’s more diversity.”

At what was billed as her first major speech before a political audience Thursday night, Cheri Daniels spoke for 20 minutes about her low-key life as first lady of Indiana. She wore a red sheath dress and regaled the audience with stories of milking cows, flipping pancakes and spitting watermelon seeds.

Molly Deuberry, a Republican who attended the speech, said she sees the Danielses as compelling. “I think the story of reconciliation is a strong story,” she said. “If anything, it kind of helps solidify them as a role model couple for the country.”

Staff writers Rachel Weiner and Anne E. Kornblut and polling director Jon Cohen contributed to this report.