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Michael Conroy, File, Associated Press
FILE - In this Nov. 2, 2010, file photo Republican Rep. Dan Burton speaks after defeating Democrat Tim Crawford for Indiana's 5th Congressional district in Indianapolis. The longtime Indiana Congressman announced Tuesday, Jan. 31, 2012, that he won't seek election for a 16th term in Congress.

INDIANAPOLIS — Indiana Republican Dan Burton, whose ardent investigations of Bill Clinton in the 1990s lifted his national profile, announced Tuesday that he is ending a three-decade career in the U.S. House due to an undisclosed family health concern.

Speaking before the Indiana House, where he began his career in elected office, Burton said he'll not run again when his term ends this year. He prevailed in tough GOP primary battles the past two elections and was expected to face another this year, but he told reporters before the speech that's not the reason for his retirement.

"I don't want to get into it, it's about personal problems with family health," he said.

Burton, who was elected to his 15th term in November 2010, doggedly pursued Clinton through the 1990s as chairman on the House Oversight and Government Reform Committee. In 1994, he told House colleagues he shot a watermelon with his rifle as part of a bizarre re-enactment of the alleged murder of Clinton aide Vince Foster.

As he grilled the former president for his infidelity during the Monica Lewinsky scandal, Burton was forced to admit to an extramarital affair after it was discovered he had a child out of wedlock.

Burton held the oversight committee gavel until 2003 after he stepped down from the chairmanship because of House Republicans' six-year term limit on running committees.

After his speech at the Indiana Statehouse, he was asked about the lapel pin he wore for the occasion. He said it was Don Quixote, a role model for him as he tilted at the occasional windmill during his long career.

"All my life I wanted to fight for the impossible dream," he said.

Indiana Republicans redrew his congressional district last year to remove some of his strongest bases of support. Meanwhile, a strong crop of contenders led by former federal prosecutor Susan Brooks and former Rep. David McIntosh has been running hard against Burton in the Republican primary race.

Burton said Tuesday he did not have any plans to endorse a successor.

He first won election in 1982 to the 5th District, which remains heavily Republican under new electoral boundaries state legislators approved last year. It includes all of Hamilton County and the north side of Indianapolis, but lost some rural counties closer to Fort Wayne that Burton carried on his way to winning the 2008 and 2010 primaries.

Former state Rep. Mike Murphy, who was among the 2010 challengers to Burton, said the redrawing of the congressional district by the GOP-dominated Legislature took away many of the voters who continued to support him — including boosting him to a 2010 Republican primary win with 30 percent of the vote in a seven-candidate field.

"The more outrageous things he did, the more that core seemed to say 'Go get 'em Dan' and a lot of that core was in the northern part of that district," said Murphy, a former Marion County Republican chairman.

Murphy said the greater concentration of the district in the northern suburbs of Indianapolis put Burton at a greater disadvantage since he had lost that area to other candidates in the 2008 and 2010 primaries.

Burton recently flew to Florida to campaign for his former boss, former Speaker Newt Gingrich, ahead of Tuesday's Republican primary there.

Murphy said he expected "a race to the finish" for the Republican nomination between former Marion County coroner John McGoff, Brooks and McIntosh.

State Sen. Mike Delph of Carmel, a former Burton aide, has been mentioned as a possible candidate, but declined Tuesday to discuss a possible candidacy. Candidates have until Feb. 10 to enter the race.

"Today is about Congressman Burton and we'll deal with all these other matters down the road," Delph said.

Delph could run safely for Congress and still run again for his state Senate seat, which is not up until 2014, if he loses. Delph, who worked as an aide to Burton from 1996-2004, said he found out about Burton's decision Monday night.

Tom LoBianco can be reached at http://www.twitter.com/tomlobianco