Do candidates' family lives matter to voters? Not much.

As fathers and husbands, Mitt Romney and Rudolph Giuliani could hardly cut more different public profiles.

Mr. Romney, the former Massachusetts governor, is still married to his wife of 38 years. His telegenic sons, daughters-in-law, and grandchildren are fixtures on the presidential campaign trail and, in public at least, a Leave-it-to-Beaver tableau of family bliss.

Mr. Giuliani, meanwhile, weathered an ugly public divorce from his second wife while involved with a double-divorcée who would become his third wife. Not only is the former New York mayor estranged from his children, but his daughter's page on the social networking website Facebook, recently discovered by reporters, exposed her as a supporter of Democratic rival Barack Obama.

But when Americans enter the voting booth to choose a president next year, how much will a candidate's family life matter? If history is any guide, say experts, not much.

"It doesn't seem to impact the ballot box," says Doug Wead, author of "All the President's Children," about first families.

Bill Clinton remained popular even after Monica Lewinsky and Paula Corbin Jones became household names. Ronald Reagan, still a hero to social conservatives, was the only divorced man elected president and had a daughter who assailed his politics and posed for Playboy.

"Billy Carter, Roger Clinton, Betty Ford – there's a long history of embarrassing siblings, wives, children," says Robert Watson, a political scientist at Lynn University in Boca Raton, Fla., who writes about first families. "Candidates ought to be thankful that the public really doesn't care."

Decline of old-fashioned values

In Pew Research Center polls this year, only 9 percent of Americans said a divorce would make them less likely to vote for a presidential candidate. The percentage who said they had "old-fashioned values about family and marriage" dropped over the past two decades from 87 percent to 76 percent.

But the willingness of American voters to overlook family scandal in an otherwise attractive candidate is not just a symptom of looser social mores.

Andrew Jackson defeated a sitting president in 1828 despite a vicious smear campaign against his wife, Rachel Donelson Jackson, who it turned out was not divorced from her first husband at the time of her marriage to Mr. Jackson.

"Grover Cleveland had a child out of wedlock, admitted he was the father, and yet Americans elected him twice as president," says Mr. Wead, referring to the late 19th-century president. "That's how tolerant the American people can be."

That may be good news for this year's crop of leading Republican hopefuls. Sen. John McCain of Arizona is remarried to an heiress and former cheerleader whom he began seeing before his divorce from his first wife. Fred Thompson, the still-undeclared actor and former senator from Tennessee was married for the second time in 2002 to a woman 24 years his junior. Romney is the only top-tier candidate still with his first wife.

"For Republicans, I'd think marital history can become an issue with the very conservative end of the party," says Dianne Bystrom, director of Iowa State University's Carrie Chapman Catt Center for Women and Politics. "But overall, voters are forgiving because all lives are messy."

Americans do have limits. A candidate who strays from his wedding vows during a campaign – and is caught – is usually history: see Gary Hart, Monkey Business, 1988.

But in the Pew polls, the biggest turnoffs in a presidential candidate – atheism and a lack of political experience – had little to do with their divorce count or the number of phone calls they get each week from their children. The most appealing traits were military service and Christian faith.

Families can help spread campaign message

If a large and intact family is useful in an election season, political historians say, it is in a more practical way: as surrogates that let a campaign be in many places at once.

Josh Romney, one of Romney's five sons, drove an R.V. – the "Mitt Mobile" – across all 99 Iowa counties this summer. Mr. Clinton has emceed fundraisers on behalf of his wife, Sen. Hillary Rodham Clinton (D) of New York. Elizabeth Edwards and Michelle Obama maintain speaking schedules apart from their husbands, former Democratic Sen. John Edwards and Senator Obama.

Giuliani's relationship with family draws scrutiny

Giuliani, on the other hand, is unlikely to get much help from his children. Andrew and Caroline Giuliani appear nowhere on his campaign website. His current wife, Judith Giuliani, frequent tabloid fodder for her sharp elbows and expensive tastes, has of late been less asset than liability.

At a town-hall-style campaign event in New Hampshire last week, Giuliani signaled that he didn't want to talk about his family.

"There are complexities in every family in America," Giuliani reportedly said, when a local woman asked how he could expect loyalty from GOP voters when his own children didn't seem to support him. "The best thing I can say is kind of, 'Leave my family alone, just like I'll leave your family alone.' "

Giuliani instead asked the audience to judge his record as a mayor and federal prosecutor, according to an Associated Press account.

Because Giuliani's popularity derives from his leadership of America's largest city after 9/11, and not an image as a family man, he may just get his wish.

"His public profile was firmly mythologized without a spouse or children," says Carl Sferrazza Anthony, author of "America's First Families." "It was like General Eisenhower during the war."