The lawmaker poised to cause the Bush administration's biggest headaches when Democrats take control of Congress may just be a grocer's son from Watts who's hardly a household name off Capitol Hill.

Rep. Henry Waxman has spent the last six years waging a guerrilla campaign against the White House and its corporate allies, launching searing investigations into everything from military contracts to Medicare prices from his perch on the Government Reform Committee.

In January, Waxman becomes committee chairman — and thus the lead congressional hound of an administration many Democrats feel has blundered badly as it expanded the power of the executive branch.

Waxman's biggest challenge as he mulls what to probe?

"The most difficult thing will be to pick and choose," he said.

The choices he makes could help define Bush's legacy.

"There is just no question that life is going to be different for the administration," said Rep. Tom Davis, R-Va., the current committee chairman. "Henry is going to be tough. ... And he's been waiting a long time to be able to do this."

Waxman, 67, is in his 16th term representing a Los Angeles district that has migrated west over the years to take in some of the country's most exclusive real estate: Bel Air, Malibu, Beverly Hills. It's worlds from the apartment he grew up in over his father's grocery store, in a predominantly black neighborhood where, he said, "There was one other Jewish kid — my sister."

The glitz of his district hasn't rubbed off. He remarks wryly that Malibu's celebrity beach-access disputes are, luckily, not a federal issue. And he's never been to the Oscars.

At first he wasn't invited, and now, "I have this reputation of never having gone." Why ruin it?

Balding, and quiet-spoken, with glasses, a snub-nose and a mustache, the 5-foot-5-inch Waxman isn't an in-your-face political bruiser. But he doesn't shrink from a fight.

At age 28 he challenged and beat a Democratic incumbent to win a seat in the state Assembly. Once in Congress, he muscled aside a more senior lawmaker to become chairman of an Energy and Commerce subcommittee, using the post to summon the heads of big tobacco to the famous 1994 hearing, depicted in the movie "The Insider," at which they testified that nicotine wasn't addictive.

"One of the biggest miscalculations of corporate America," Waxman now calls that.

Waxman also protected and strengthened the Clean Air Act, expanded Medicaid coverage for poor children and wrote a landmark AIDS care bill. Then Democrats lost control of Congress in 1994.

The minority party in the House has few rights, and Democrats have complained that GOP leaders completely shut them out from writing legislation.

So, Waxman said, "I recreated myself as an investigator."

The makeover was a success.

When he became top Democrat of the Government Reform Committee in 1997, Waxman realized that he didn't have to settle for playing defense like most in the House minority. He took advantage of the committee's large staff to hire talented investigators to pursue projects large and small.

His targets have ranged from why the Taekwondo Union was allowing 12- and 13-year-olds to kick opponents in the head, to Medicare drug costs and baseball steroid use, to abuse of Iraqi prisoners at Abu Ghraib and government contracts given to Vice President Dick Cheney's former company, Halliburton.

After agitating by Waxman, the State Department had to revise a report claiming terrorism had decreased in 2003, to reflect that it actually had increased.

Waxman found overbilling on Katrina contracts and overbilling by Halliburton in Iraq. He revealed that seniors wouldn't really save on premiums by switching to the government's Medicare drug plan. With Davis, he issued a report documenting extensive contacts between the White House and convicted lobbyist Jack Abramoff. The Taekwondo Union agreed to prohibit head kicks by anyone under 14.

And when Bush administration resistance meant he didn't get results, Waxman got headlines for trying.

As Government Reform chairman, Waxman will aim to reassert congressional checks on the executive branch. A priority are government contracts: for Hurricane Katrina cleanup, homeland security and the Iraq war.

Contrary to Republican portrayals, Waxman said he doesn't plan to issue scattershot subpoenas. He said he has little interest in revisiting Bush administration failures that are already well known, such as Iraq war intelligence.

He wants to do it all with the help of Republicans.

"We want to return to civility and bipartisanship," Waxman said. "Legislation ought to be based on evidence, not ideology."