Rep. Issa tested by the spotlight WASHINGTON - During the 2010 campaign, Rep. Brad Sherman, a Democrat from Sherman Oaks, joked, "Every time I try to encourage the White House to do more to help us elect Democrats to the House of Representatives, I send them a picture of Darrell Issa with the word 'subpoena' underneath." Issa, who has headed the House's top investigative committee since his party won control of the chamber in 2010, has lived up to Sherman's expectations. The Republican from Vista in San Diego County has become the Obama administration's chief antagonist in Congress. He is praised by Republicans for aggressively rooting out government waste and abuse and putting the White House on the defensive, and accused by Democrats of exploiting his high-profile position for partisan advantage. As Issa prepares to lead a House Oversight and Government Reform Committee hearing Wednesday on the Internal Revenue Service scandal, he will be in a place he loves - the spotlight. But he faces a delicate balance: to investigate the agency's now-repudiated practice of targeting conservative groups for extra scrutiny, and do it without overreaching. "This will be a good test for him," said former Rep. Tom Davis (R-Va.), a onetime oversight panel chairman. You don't want to be out in front of the facts. The IRS hearing comes at a time of already strained tensions between congressional Republicans and the White House, heightened by Issa's dogged investigation into how the Obama administration handled the Sept. 11 attack on the U.S. diplomatic outpost in Benghazi, Libya. Last week, Atty. Gen. Eric H. Holder Jr., a frequent target, engaged in a testy exchange with Issa, who repeatedly cut Holder off. Holder denounced the way Issa conducts himself as a congressman as "unacceptable" and "shameful." Issa, in an interview, calmly shrugged it off. "He was under a lot of pressure," he said of Holder. He's got a lot of problems going on. Issa needs to take care that his reputation as a particularly partisan Republican does not undermine the legitimacy of the investigation, Princeton University historian Julian Zelizer said. "He needs to make sure that this doesn't turn into a witch hunt - that he and his allies don't make more of what happened than they should," he said. If they turn a sloppy IRS office into Watergate, this will surely backfire on the GOP, especially with Issa leading the charge. Issa says he will follow the evidence wherever it leads. A grandson of Lebanese immigrants, Issa rose from a teenager charged with stealing a red Maserati (he denied the charge, and the case was dismissed) and high school dropout (he joined the Army, later earning a college degree) to an entrepreneur who amassed a fortune by manufacturing and selling car alarms. Issa's voice can still be heard on alarms warning: "Protected by Viper. Stand back. The Center for Responsive Politics estimates that he is the second-richest member of Congress, with a net worth at $216 million to $745 million. Issa, 59, spent $9 million of his money in an unsuccessful bid for the Republican nomination for the U.S. Senate in 1998. He spent another $1.7 million for the petition drive that led to the 2003 recall of Democratic Gov. Gray Davis, but dropped plans to run for governor after Arnold Schwarzenegger declared his candidacy. Issa says he has no plans to seek higher office at the moment, noting that his 12 years in Congress have put him in a position to influence policy. "I'm doing the job I want to do," he said. His committees and subcommittees have conducted more than 200 hearings on a variety of subjects, including the government's botched Fast and Furious gun-trafficking surveillance operation. The titles of some hearings, such as "How Obama's Green Energy Agenda Is Killing Jobs," have contributed to accusations that he has been partisan. Issa says such criticism comes whenever the oversight committee investigates an administration led by the opposing party. "What could he do that wouldn't be viewed as political?" asks Rep. Jason Chaffetz (R-Utah), an oversight panel member. Rep. Henry A. Waxman (D-Beverly Hills), former oversight committee chairman, often sparred with the George W. Bush administration. In an interview last week, Waxman accused Issa of being "overly partisan" and using the panel "not to really dig into issues, but to go after the Obama administration and Democrats." Rep. Elijah E. Cummings of Maryland, the committee's top Democrat, has clashed with Issa, but declined to talk about him. Issa has regularly tangled with the Obama administration, most notably in accusing Holder of lying to Congress and refusing to turn over documents. He persuaded the House to hold Holder in contempt of Congress. Issa was widely criticized - and ridiculed on "Saturday Night Live" - for opening a hearing related to contraception with a panel of male witnesses. Issa said the hearing was focused on religious liberty, specifically a requirement for religion-affiliated institutions to offer employees birth-control coverage. Despite his fearsome reputation, Issa has led efforts to pass bipartisan legislation, including measures to strengthen protections for government whistle-blowers. And he conducted an investigation of Countrywide's use of loan discounts to curry favor with government officials, referring the names of lawmakers from both parties to the House Ethics Committee. Although the ethics panel closed its investigation, Issa said his inquiry sent "an unmistakable warning to any entity that might try to duplicate Countrywide's lobbying strategy."