Yet Corbett, 60, says he is running just as hard as he did in 2004, when he first won statewide office in a brutal and demanding race.
He has even asked his daughter to push back her wedding by a week so it falls after next Tuesday's Republican primary.
"I always worry," the state's top prosecutor said during a recent interview. "I don't take anything for granted."
That mantra has carried Corbett far during his relatively short political career.
Except for a stint as a town commissioner in the 1980s, the Republican from Pittsburgh spent most of his career as a prosecutor or in private law practice before running for attorney general in 2004.
Yet for someone who has spent little time in elected office, he has emerged as one of the more recognized - and controversial - figures in Harrisburg.
The notoriety stems in large part from the legal case that has come to define his career as the state's top lawyer: the wide-ranging corruption investigation known as Bonusgate.
"It put him on the map," said political analyst William Green of Pittsburgh.
Under Corbett, the Attorney General's Office has charged 25 people, including current and former legislators, with using state resources (ranging from state employees to taxpayer-funded software programs) for political campaign work.
The investigation has thus far resulted in three convictions, two acquittals, and seven guilty pleas and has earned Corbett the kind of publicity most candidates have to pay for.
The case has also amassed its share of detractors who say Corbett has crushed careers - sometimes unfairly - to further his own.
He brushes aside such talk.
"I didn't go into office looking for this," he said. "We created a public corruption section in the Attorney General's Office, but I never thought they'd be this busy."
Corbett says he did not seriously start thinking about running for governor until 2008, when he handily won reelection as attorney general. It was an impressive showing for a Republican amid the onslaught of new Democratic registrations prompted by enthusiasm that year for Barack Obama's candidacy.
The victory did not just convince Corbett, it became a clarion call among top Republicans: They could no longer ignore the prosecutor who, until then, was considered smart and aggressive but not ready for prime time.
"He was always a contender . . . but that shot him out of the cannon," said Bob Asher, the Montgomery County-based GOP power broker who soon thereafter threw his support behind Corbett's gubernatorial run.
His path was not always so clear. As a lawyer's son growing up in suburban Pittsburgh, he hardly gave a thought to running for office.
"Tom was sort of a late bloomer," said his wife, Susan Corbett, an executive with the nonprofit Gettysburg Foundation, which works to enhance and preserve Gettysburg's heritage. "I don't know that he knew what he wanted to do until midway through college."
The greatest influence
His father was a lawyer. But the greatest influence on Corbett's young life was his mother, who had three-quarters of her stomach removed when he was 10.
She was a stay-at-home mother who battled cancer for years until she died of a heart attack when her son was a senior in high school.
Though she was not an alcoholic, Corbett said, his mother drank to lessen the pain.
"To this day I can't stand the smell of bourbon, because she would drink bourbon," he said.
No one, he said, has left a bigger stamp on his life.
"She taught me to be fair," Corbett said. "I haven't forgotten that lesson."
He went to law school at St. Mary's University in San Antonio. He began his career as an assistant district attorney in Pittsburgh and stayed in that job four years before becoming an assistant U.S. attorney there in 1980.
"He was a terrific trial lawyer," said Common Pleas Court Judge Jeffrey A. Manning of Allegheny County.
"He had this ability to sift through complicated evidence and figure out exactly what occurred," added Manning, who worked with Corbett both in the District Attorney's Office and as a federal prosecutor.
Corbett left the U.S. Attorney's Office in 1983 for private practice, in part because he wanted to dabble in politics.
In 1988, a top Republican Party official asked him to chair Vice President George H.W. Bush's Western Pennsylvania presidential campaign.
It turned out to be a smart career move and put his name on the political radar. When Bush took office as president, his administration appointed Corbett the U.S. attorney in Western Pennsylvania, a job Corbett held until Bill Clinton replaced Bush.
Several years later, Gov. Tom Ridge appointed Corbett to fill the unexpired term of Attorney General Ernie Preate Jr., who resigned in connection with his guilty plea to a federal mail-fraud charge. As part of his appointment, Corbett promised not to run for a full term in the office Preate was vacating.
But years later, he got the bug again for the job - and narrowly won it in 2004, gout and migraines notwithstanding.
He beat out Democrat Jim Eisenhower, a former assistant U.S. attorney in Philadelphia.
In an interview, Eisenhower called Corbett a tough competitor but criticized the Republican for being vague on issues and light on detail.
Eisenhower said Corbett will have to demonstrate that he is interested in tackling problems beyond the scope of the Attorney General's Office.
"What does he know, and what is his experience with issues that a governor deals with? That's something he's going to have to explain," said Eisenhower, who has also represented a key witness in the Bonusgate prosecutions.
The criticism grates on Corbett.
"What do they think we do?" he asks. "Every day [as attorney general], I manage a budget of over $100 million, I have to deal with other agencies in state government on a regular basis. I manage every day. But more importantly, an executive has to make tough decisions."
On the campaign trail, Corbett has espoused a traditionally Republican platform - although observers note he has tilted somewhat further to the right in an apparent nod to the tea party movement. (Corbett's opponent in the GOP primary, State Rep. Sam Rohrer of Berks County, has aired radio ads calling himself "the authentic conservative.")
As governor, Corbett says, he would cut or phase out various corporate taxes to create a friendlier business environment, attract new enterprise and create jobs.
He has also taken a no-new-taxes pledge and said he would require state agencies to review all programs related to economic development to ensure their effectiveness.
Corbett opposes abortion and same-sex marriage, and he supports gun rights.
He has said federal stimulus dollars should only have been used for infrastructure. And he is among 14 state attorneys general suing to overturn the federal health-care law signed by President Obama.
As attorney general, Corbett has aggressively pursued child predators who prowl the Internet and scammers who victimize the elderly.
But it is Bonusgate that has defined his time at the helm. The investigation has led to corruption charges against Republicans as well as Democrats.
It has also spawned a small but vocal universe of bloggers and Twitter users who daily bash Corbett and his investigation as politically motivated, though some of these writings are suspected to have originated with defendants in the Bonusgate case.
They are not the only ones throwing darts. A liberal-leaning group called Keystone Progress has also pounded Corbett for filing suit against the health-care law.
"We believe it's a political move," said Michael Morrill, Keystone Progress' executive director, who has called for Corbett to resign. "An attorney general needs to be above reproach."
Again, Corbett shrugs off the criticism. "It's a free country," he says. "They can say whatever they want to say. Do I like it? It doesn't matter."
He knows the criticism will only get louder if he wins the party's nomination next Tuesday. But Corbett says he has never second-guessed his decision to run for governor.
"You have to have bulldog determination," he says. "If you don't have it, then get out of the game."
Contact staff writer Angela Couloumbis at 717-787-5934 or email@example.com.
Age: 60. Born June 17, 1949, in Philadelphia.
Education: Bachelor's degree in political science, Lebanon Valley College, 1971; law degree, St. Mary's University School of Law, San Antonio, Texas, 1975.
Professional experience: Assistant district attorney, Allegheny County, 1976-80; assistant U.S. attorney, 1980-83; private practice, 1983-89. U.S. attorney for Western Pennsylvania, 1989-93; private practice, 1993-95; chairman of the Pennsylvania Commission on Crime and Delinquency, 1995-2003.
Political experience: appointed state attorney general to fill unexpired term, 1995-97; elected attorney general, 2004-present.
Family: Wife, Susan. Two grown children, Katherine and Thomas.