But the 80-year-old New Mexico political giant's persona was shaken Wednesday with the revelation that he had an out-of-wedlock child in the 1970s and became embroiled in what might be described as an inside-the-Beltway soap opera.
While his wife Nancy was raising their eight children, Domenici had the affair and secret child with a woman about half his age—and who happened to be the daughter of one of his Senate colleagues. The woman raised the child on her own, became a prominent lobbyist, Republican activist and political commentator, and their 30-something son has since gone on to build an impressive Washington resume himself.
The saga shocked people in New Mexico who viewed Domenici as a man of honesty and integrity during his six terms and 36 years in the Senate that ended in 2008.
"I deeply regret this and am very sorry for my behavior," Domenici said in his statement. "I hope New Mexicans will view that my accomplishments for my beloved state outweigh my personal transgression."
Domenici and the mother of the child, Michelle Laxalt, went public this week, she said, out of fear someone was about to release the information in an attempt to smear Domenici and his "extraordinary wife." They issued a statement revealing the story to the Albuquerque Journal.
They identified their son as Nevada attorney Adam Paul Laxalt, a former U.S.
It was just the latest in a seemingly endless stream of politicians being forced to reveal secret children, from one-time Democratic presidential candidate John Edwards to former Republican Gov. Arnold Schwarzenegger. Just last week, U.S. Rep. Steve Cohen of Tennessee acknowledged that he's the father of a 24-year-old woman after the two were seen communicating on Twitter during the State of the Union address.
Domenici was known for his unflagging support of the state's national laboratories and military installations, and he became a power broker for his work on the federal budget and energy policy.
Domenici voted for the impeachment of former President Bill Clinton in 1998 after his affair with Monica Lewinsky, but his floor statement focused on the fact that Clinton had lied under oath, noting that the trial "has never been about the President's private sex acts, as tawdry as they have been."
But in the same speech, he cited the value of "truthfulness" and how it's the first pillar of good character.
Reached at his home in Washington on Wednesday, Domenici said he had nothing more to say. Domenici and his wife have been married more than 50 years and have eight children.
Michelle Laxalt was an up-and-coming Washington figure when she and Domenici had an affair. Laxalt, then in her 20s, is the daughter of former Nevada Gov. and Sen. Paul Laxalt, who served two terms beside Domenici.
In 2008, Domenici was reprimanded by the Senate ethics committee for his involvement in a scandal over the Bush administration's firing of eight U.S. attorneys.
At the time, Laxalt defended Domenici's integrity on CNN, calling him an honorable man who was supporting "no fewer than eight children."
The website for Adam Laxalt's law firm said he is a former U.S. Navy officer and lawyer who served in Iraq. He also worked for then-Sen. John Warner, R-Va., and as a special assistant to an undersecretary of state, according to the website.
He has also written a number of conservative columns against policies like the Obama health care plan and the lifting of the military's "don't ask, don't tell" policy for gays for publications like The National Review Online, American Spectator and the Las Vegas Review-Journal. And he serves on the board of Catholic Charities of Southern Nevada.
Domenici said he was sorry that he caused hurt and disappointment for his wife and other family members. He said he disclosed the situation to his family several months ago.
"I have apologized as best as I can to my wife, and we have worked together to strengthen our relationship," Domenici said.
Domenici told the Journal his son participated in the drafting of his statement, but it was unclear if the two had a prior relationship.
The Laxalts did not immediately respond to emails and phone calls seeking comment.
In New Mexico, political leaders said they were surprised, but they doubted the revelation would negatively impact the Domenici legacy.
"It is going to make his legacy a little bit more colorful because he is not exactly the kind of guy you expect that from," said Maurilio Vigil, a political science professor emeritus at Highlands University in Las Vegas, N.M.
"It is surprising because he was always an upstanding type of fellow, a family man, and that was his image."
Edward Lujan, former chairman of the Republican Party of New Mexico, said he had heard rumors about the child years ago, but "I didn't pay much attention. I didn't care. Those kinds of things honestly are between the families and has nothing to do with how he did his job."
"I don't think there was anything hypocritical about anything," Lujan said. "I admire him as much today as I did yesterday and the day before."
Republican Gov. Susana Martinez said her "thoughts and prayers are with the family.
"It's a difficult time," she said, "but Sen. Domenici's work is a very separate and distinct issue. I think he's done great things for the state and I don't think anyone will ever forget the hard work and all that he brought to New Mexico."
Others weren't as strong in their defense of Domenici and sizing up how the revelations would affect this legacy.
"I'll leave that for historians and other people to judge," said former Gov. Toney Anaya, a Democrat who ran a close race against Domenici in 1978.
Associated Press writers Russell Contreras and Barry Massey contributed to this report.