June 9, 2010 -- Before his four-decade career in politics, Jerry Brown briefly entered a Jesuit seminary. It is that monkish sense of austerity with which the California Democrat plans to run against a billionaire Republican gubernatorial opponent with virtually bottomless coffers.

If elected, Brown, 72, will be the oldest sitting governor in the United States. A fixture of California politics and the state's current attorney general, Brown was governor from 1975 to 1983 and ran three unsuccessful presidential campaigns.

"It'll be a tough fight. Maybe the toughest," Brown said of the upcoming general election against newly minted Republican candidate Meg Whitman, the former CEO of eBay who spent $80 million during the primary and has pledged to spend as much as $150 million of her own money in her bid to become governor.

"I'm going to be as frugal as I can," Brown told ABC News' Diane Sawyer. He used the words "frugal" or "frugality" several times in the course of the brief interview. Austerity, he said, begins at home.

"We need now to reset," he said. "So austerity, some frugality, and I know how to do that. When I was governor, I got rid of the jet. I didn't live in the mansion."

"Are you going to do that again," asked Sawyer. "No plane for you? No mansion for you again?"

"No," said Brown. "Well, there is no mansion."

Brown said he is prepared for a difficult battle in which Whitman will blitz California's airwaves and voters' mailboxes with a message that is fiscally conservative and promises job creation.

"Every hour, maybe every 15 minutes, everyone's going to hear the opponent's message. That is quite extraordinary," he said.

Brown, just a day after winning his party's nomination, went on the attack, assailing Whitman's lack of political experience, the timing of her pay raises as CEO, and her record on job creation in the private sector. He claimed some jobs she was created were "exported" out of the state. Meg Whitman declined to be interviewed by ABC News.

During her speech accepting the Republican nomination on Tuesday, Whitman launched her own opening salvo against Brown, calling him a career politician and lambasting his record on employment and education while in office.

"Jerry Brown has spent a lifetime in politics, and the results have not been good," she said. "Failure seems to follow Jerry Brown everywhere he goes. It's a record of promising much and delivering little, of saying one thing, and then doing quite another."

She blamed Brown for high unemployment and massive state spending during his two terms as governor from 1975 to 1983 and for Oakland's poor performing schools when he served as that city's mayor from 1998 to 2006.

In a November interview with ABC News, Whitman said: "If you want a different approach, if you want a more business-like approach, if you want someone who knows how to create jobs, and knows how to focus, then I'm your person. If you want a different person, then you should vote for that. But I will talk about my strengths in this race, which is different from a career politician, Jerry Brown or otherwise."

Brown used a question about whether he would take an unpopular position within his party against organized labor to compare the difficulties of being a state executive against those of being a corporate executive.

"When I was governor, when I saw an excessive employee pay raise, I vetoed it -- not once, but twice," he said. "I know how to stand against the storm. This is not like being a CEO, where you're in a private board room. You got the media. You've got the opposition party. You have a lot of emotions.

"We're in trouble," he said of California, a state with one of the world's largest economies and a $6 billion deficit. "California is in a mess."

Brown said companies that hire new employees should be entitled to tax credits, but he opposed Whitman's plan to give tax breaks to the wealthy.

"[Whitman is] going to cut all the taxes on the rich, like herself, and that'll somehow create jobs," he said. "That'll increase and exacerbate the gap."

A counterculture icon of the 1970s, Brown was nicknamed Gov. Moonbeam for a proposing the state buy a communications satellite.

Brown said even at 72, he has no lack of energy. He runs and does pull-ups every morning, he told Sawyer.

A former seminarian who studied Buddhism in Japan and a volunteered in India with Mother Theresa, Brown found a spiritual message in his campaign.

"Well, at the end of the day, what really is this all about?" he asked. "The fundamental quest is: How do we touch our spirituality? How do we touch that innermost part of our being? And how are we open to that same thing in other people?

"That's the intimacy, the spirituality, that you don't normally find in politics," he said. "But it's the other side. After everything quiets down, you're still yourself. And there's still life and death. When I was studying in Japan, before you'd mediate ... in the evening, someone would hit a block a few times. And then someone would intone: 'Life and death is a serious matter. Time waits for no man. Do your best.' And that, I think, could be the spirit of this campaign."