copyright 2009, The Washington Post WASHINGTON -- Sen. Joseph Lieberman gaveled into session Capitol Hill's first public hearing on the Fort Hood attack, promising Thursday to run his investigation from exactly where he sat on the dais -- the center. The homeland security committee inquiry would be conducted in a 'bipartisan and nonpartisan way,' he said, which seemed fitting for the longtime Connecticut Democrat who won as an independent in 2006, backed a Republican for president in 2008 and does not know what he will be by the time his 2012 reelection contest comes around. Lieberman has built a career straddling party lines, but as an independent he has taken to new heights the art of leveraging clout from the center. His latest focus: the debate over health-care reform and, now, the investigation into the shootings on the Texas military post that left 13 dead and dozens wounded. Other committee chairmen, all of them Democrats, have held off on launching inquiries, mindful of the Obama administration's requests that lawmakers slow down as the White House conducts its review. Some Republicans, particularly in the House, have essentially accused the White House of a cover-up. Lieberman sits somewhere in between. 'Some people have jumped to attack the administration for wanting to stop the investigation,' he said in an interview Thursday. 'My way of operating here ... is to work with the administration and proceed cooperatively as opposed to going into an attack mode.' Some on the left don't see it that way. Daily Kos, an influential liberal blog, featured two posts on Lieberman on Thursday, one an attack on his 'Fort Hood political theater' and the other an expletive-laden tirade against his position on health-care reform. As the Senate nears consideration of its compromise health bill, Lieberman has drawn increased scrutiny for threatening to filibuster any reform bill that includes a public insurance option. He is sensitive to criticism that he is simply siding with Republicans, and he told National Public Radio on Wednesday that he was doing what he believed and not seeking to 'join with anybody in any political party.' Lieberman first angered many on the left with his support of the Iraq war and most of the Bush administration's national security policies. After losing the 2006 Democratic primary, he further inflamed liberals by winning reelection anyway as an independent. Then he strongly backed Sen. John McCain, R-Ariz., in the 2008 presidential campaign and had even been considered a possible running mate. But after a brief controversy last year over whether he should keep his committee post, Lieberman has been a largely reliable vote for Democrats. 'He's been very constructive,' Sen. Chris Dodd, D-Conn., said of Lieberman's role in the health-care debate, adding that Lieberman was taking less heat from his colleagues than advertised. 'A lot more are made of these things than are actually the case,' Dodd said. Lieberman's future in the party -- and the Senate -- remains unclear. He could try running in 2012 as a Democrat but risks losing the primary again. He could run as an independent or retire. Republicans would love to have him in their caucus, but he shows no signs of wanting to switch parties. 