WASHINGTON Just who is Newt Gingrich anyway?

Is he the big thinking rhetorical bomb-thrower who led Republicans to power in the House of Representatives in 1994 for the first time in four decades, only to have his troops rebel against him four years later?

Is he the undisciplined, self-absorbed House speaker who admitted that a 1995 shutdown of the federal government was prompted in part by what he perceived as a cold shoulder and shabby treatment by President Bill Clinton during a long Air Force One flight?

Is Gingrich the do-as-I-say-not-as-I-do leader who pushed for Clinton's impeachment in 1998 stemming from his affair with White House intern Monica Lewinsky even while having an affair of his own with a congressional aide?

Or is he the professorial, adult in the room, elder statesman seen on TV during this year's Republican presidential debates - a forum that's helped catapult him from the bottom tier to the top rank of GOP White House hopefuls? Gingrich now leads in national and early-primary-state polls and is increasingly viewed as the top conservative alternative to the other front-runner, former Massachusetts Gov. Mitt Romney.

"Anybody who looks at me as a 68-year-old grandfather and says, 'All right, has he grown wiser, has he learned from his experiences, is he somebody that I would trust to lead the American people?' " Gingrich said recently on Fox News' "Fox & Friends." "They've got to come to their own judgment about that."

As he seeks the Republican presidential nomination, even Gingrich concedes that choice could be a difficult call for voters, as his life - both political and personal - has been a rollercoaster ride of soaring highs and messy lows.

"My tenure as Speaker has been marked by both unprecedented accomplishment and unprecedented conflict," Gingrich penned in the liner notes to "Lessons Learned the Hard Way," his 1998 mea culpa book. "I have learned some difficult lessons that will shape my outlook forever."

Speaker of the House

Gingrich has been hailed for being a brilliant political strategist who authored the "Contract with America," a 10-point conservative legislative agenda that served as the cornerstone for the GOP takeover of the House in 1994.

As speaker, Gingrich played a significant role, along with the Clinton White House, in revamping the nation's welfare system and balancing the federal budget, his supporters say.

"He focused on those things," said former Rep. Robert Walker, R-Pa., a Gingrich friend and campaign surrogate. "Newt does spin out ideas like every minute because he thinks that way. Sometimes it comes off that he's not focused, but he is, and has accomplishments to prove it."

But he earned a reputation as a hyper-partisan, polarizing figure from his sharp attacks on Speaker Jim Wright, D-Texas, which produced an ethics investigation into Wright and led to his resignation in 1989.

Gingrich later went through an ethics probe into his own activities that in January 1997 resulted in him becoming the first speaker to be reprimanded by the House. He was forced to pay a record $300,000 fine for violating tax law and lying about it to the House Ethics Committee.

A few of his lieutenants engineered a failed coup against Gingrich in late 1997. By the end of 1998, a battle-weary Gingrich had had enough. He quit as speaker and didn't seek re-election to Congress, saying of his Republican caucus, "I'm willing to lead, but I'm not willing to preside over people who are cannibals."

A changed man?

"Newt Gingrich is one of the most complicated public figures of our day," former Rep. Susan Molinari, R-N.Y., wrote in her 1998 book "Representative Mom: Balancing Budgets, Bill and Baby in the U.S. Congress." "Incredibly smart and pragmatic, he is at his best when he is building a team. He is at his worst and most self-destructive when he swells with his own sense of invulnerability and moves to the front and center."

Sen. Tom Coburn, R-Okla., who served with Gingrich in the House, suggested in May that the former speaker should "keep his mouth shut" after he dismissed House Budget Committee Chairman Paul Ryan's Medicare overhaul proposal as "right-wing social engineering."

"You know, he used to have a little deal in his office that said 'listen, learn, and lead,' " Coburn told ABC News in May. "And he rarely followed it. He went the other way. And instead of ready, aim, fire - you got fire, ready, aim."

However, some Gingrich watchers insist that he's a changed man, humbled by his mistakes, tempered by time, and mellowed by devotion to his wife, Callista, and his conversion to Catholicism.

He remains ever the caustic combatant eager to stick it to a Democratic, or Republican, challenger, but he's not the self-imploding leader he once was, they say.

From teaching to politics

Newton Leroy McPherson was born June 17, 1943, in Harrisburg, Pa., the son of a teenage mother and a mechanic father. Their marriage ended in three days, after Newton McPherson, Gingrich's father, struck his wife, Kathleen, as she tried to wake him for work after a long night of drinking and shooting pool.

"We were married on a Saturday and I left him on a Tuesday," Kathleen "Kit" Gingrich told The New York Times in 1994. "I got Newtie in those three days."

Three years later, she married Robert Gingrich, an Army artillery officer who legally adopted young Newt, who took his stepfather's last name.

Gingrich, who holds a bachelor's degree from Atlanta's Emory University and his master's and doctorate from Tulane University in New Orleans, settled in as a history professor at West Georgia College - now called the University of West Georgia - but longed for elective office.

He ran for a House seat twice and lost. He won in 1978 by defeating a Democratic state senator, Virginia Shapard, who planned to commute to Washington and keep her family in Georgia. Gingrich's campaign slogan: "When elected, Newt will keep his family together."

Two years later, Gingrich's 18-year marriage to the Jacqueline Battley - his former high school teacher - ended in divorce. He married Marriane Ginther in 1981, but that union dissolved in 1999 in part because of Gingrich's extramarital affair with Callista Bisek, whom he married in 2000.

Callista Gingrich is a force in Gingrich's life, friends and associates say. She's an active partner in her husband's endeavors, from campaigning to his books and movie projects. He, in turn, actively promotes her works, which include a recently published children's book "Sweet Land of Liberty."

Gingrich's post-Congress life has been very lucrative. Able to command $60,000 per speech, he earned $2.5 million last year, according to his financial disclosure form. He created a universe of for-profit enterprises that include his consulting business, a historical-documentary production company, a communications firm and a literary agency. The collection of endeavors produced almost $100 million over the last 10 years, according to The Washington Post.

Baggage and all

Gingrich is aware that he has enough baggage to sink his candidacy, and he's making attempts to lighten the load. He added a section on his campaign website dedicated to addressing attacks against him.

It calls a story that Gingrich asked his first wife for a divorce while she was hospitalized for cancer a "vicious lie" and points to a piece written by conservative columnist Jackie Gingrich Cushman, his daughter, in which she calls the story false.

Gingrich considers revisiting various controversies the price of doing business to win the Republican nomination and the White House.

"When you go from also-ran to one of the two front-runners, you're inevitably going to get a huge amount of scrutiny," he told USA Today in November. "You have to. It's the presidency. It would be dereliction of duty not to."