Nancy Reagan spent decades protecting the legacy of her husband, but some of President Ronald Reagan's famous political advice appears lost among the White House candidates who embrace him as a guiding light.
It's known as the 11th Commandment: Thou shall not speak ill of any fellow Republican.
The former first lady's death Sunday in Los Angeles closed the Reagan era at a time when crude insults, appeals to extremism and locker-room braggadocio have shaped the party's 2016 presidential primary, a clashing image with the sunny "Morning again in America" theme Reagan employed as a candidate a generation ago.
The 40th president didn't author the advice about restraint on the campaign trail, and he didn't always follow it to the word, but he recognized the GOP needed to avoid infighting that could lead to a splintered party and a November defeat.
A former California Republican chairman, Gaylord Parkinson, coined the phrase in the mid-1960s to tamp down bickering between political factions in Reagan's first run for governor. A similar split between conservatives and moderates contributed to Barry Goldwater's defeat in the 1964 presidential election.
In his autobiography, "An American Life," Reagan wrote of his campaign for governor: "It's a rule I followed ... and I have ever since."
Reagan recognized that the Republican Party was not going to win unless the sides united, biographer Lou Cannon said.
Donald "Trump has blown this up and all the others have piled in. One could argue this would be a good time to restore it, but it isn't going to happen in this election," Cannon said.
"It's hard for me to see how they cannot pay a price for it," he added.
Nancy Reagan's death "reflects the symbolic passing into history of the markers established by the former president for campaigns to have certain standards which should never be breached," former Reagan campaign aide and speechwriter Kenneth Khachigian said.
"It seems like a bad dream to turn on the debates and hear the degrading dialogue," Khachigian said in an email, describing the campaign as "heartbreaking."
Since Reagan's death in 2004, Republican presidential candidates often claim to be his rightful heir, hold him up as a patron saint or outline proposals they say he inspired.
Ted Cruz calls himself the first true conservative running for president since Reagan and has promised to employ a "Reaganite" approach. Jeb Bush, now out of the campaign, called his tax-cut plan "Reagan-inspired." And Trump has alluded to Reagan's political shift — the former actor was once a Hollywood Democrat — to defend his own conservative makeover.
Reagan's depiction on the presidential campaign trail can often be at odds with the record.
Reagan is seen as an apostle of lower taxes, but during his years as governor, from 1967 to 1975, he supported what was then the largest tax increase in California history. Cutting deals with Democratic leaders in Congress, he slashed and raised taxes during his White House days.
Reagan never presented a balanced budget to Congress. A 1986 law he signed established a one-year amnesty program for people who entered the U.S. illegally and had been in the country at least four years.
In recent days, the Republican presidential campaign has become increasingly foul-toned, as candidates and the Republican establishment look for ways to slow Trump's momentum.
Former nominee Mitt Romney called the front-runner "a phony, a fraud" inclined to "absurd third-grade theatrics." In response, Trump called him a failed candidate. Trump repeatedly refers to Sen. Marco Rubio as "little Marco," while Rubio has called Trump a con man. Cruz has called Trump "part of the corruption in Washington."
The boorish spectacle of the race dismayed many visitors at the Reagan library in Simi Valley. Reagan's efforts to broaden and unify the party are commemorated at the hilltop site, where Nancy Reagan will be buried beside him Saturday. The GOP candidates may attend her funeral.
"With what's going on now with the Republicans, I'm hoping they can learn about class and tact from Nancy Reagan," said Jonathan Kritzer of Moorpark, a Los Angeles suburb. "They're tearing themselves up out there."
Sharon Hirtzer said she hopes the former first lady's death "puts the focus for the Republican Party on the greatness of Ronald Reagan."
"The level of the rhetoric has been extremely negative," the Chicago resident said of the candidates.
Associated Press writers Chris Weber in Los Angeles and Scott Bauer in Madison, Wisconsin, contributed to this report.