-LRB- CNN -RRB- -- The White House insists that it was entirely former Sen. Tom Daschle 's decision to withdraw his nomination , but some observers say he did n't have a choice . Tom Daschle said Tuesday that he 's stepping aside as the nominee for secretary of health and human services . Despite the controversy over his tax records and his work in a field that some consider lobbying , Daschle was expected to be confirmed . His withdrawal shocked Capitol Hill , and Democratic colleagues expressed regret over his decision . `` I think one of the major factors had to be that the political climate has changed radically just in the last couple of weeks , '' CNN Senior White House Correspondent Ed Henry said . President Obama ripped Wall Street executives last week for their `` shameful '' decision to hand out $ 18 billion in bonuses in 2008 while accepting federal bailout money . The next day , news broke that Daschle had n't paid his taxes in full . Daschle said Monday that he was `` deeply embarrassed '' for a series of errors that included failing to report $ 15,000 in charitable donations , unreported car service and more than $ 80,000 in unreported income from consulting . Daschle recently filed amended tax returns and paid more than $ 140,000 in back taxes and interest for 2005-07 . `` That , in this political climate , really tripped up Tom Daschle because it looked awful politically for this White House , '' Henry said . In an interview with CNN 's Anderson Cooper on Tuesday , Obama said he made a mistake in handling the nomination of Daschle . `` I think I screwed up . And , I take responsibility for it and we 're going to make sure we fix it so it does n't happen again . `` Ultimately , I campaigned on changing Washington and bottom-up politics , '' Obama said . `` And I do n't want to send a message to the American people that there are two sets of standards -- one for powerful people and one for ordinary folks who are working every day and paying their taxes . '' At a news conference Tuesday afternoon , press secretary Robert Gibbs insisted that the White House did not pressure Daschle to step down . Watch Gibbs answer questions about Daschle 's move '' Pressed on whether Daschle was given any sort of signal to resign , Gibbs said , `` I do n't know how much more clear I could be . The decision was Sen. Daschle 's . '' A Daschle ally familiar with his thinking said Tuesday that he was not aware of any White House pressure on the former Senate majority leader to withdraw his nomination . Asked whether Daschle was pushed , the source said , `` things do n't work that cleanly . '' The issue was not whether Daschle could `` survive '' ; it was what that process `` would do to Obama '' and his health care reform and economic agenda . It 's a question of the `` price of that confirmation , '' he said . The source said Daschle read the Tuesday New York Times editorial urging him to withdraw from consideration but would not say whether that might have played a part in his decision . `` Tom has been a politician for a very long time , '' the source said . `` He understands this town . He made a mistake ; he apologized , but timing matters . There was a critical mass building . '' Obama senior adviser David Axelrod said he thought Daschle made the decision Tuesday morning . `` I have to believe that Sen. Daschle having spent as many years as he has up here had a clear picture that there was going to be a delay , and I think he did n't want to contribute to that . In announcing his withdrawal , Daschle said it was an honor to be chosen to lead the reform of America 's health care system . `` But if 30 years of exposure to the challenges inherent in our system has taught me anything , it has taught me that this work will require a leader who can operate with the full faith of Congress and the American people , and without distraction , '' he said in a statement . `` Right now , I am not that leader and will not be a distraction . '' Mark Preston , CNN 's political editor , pointed out that Daschle has a `` history of making 11th-hour decisions . '' Six years ago , Daschle made a last-minute decision not to run for president after he had been all set to go . `` I think that the Tom Daschle we saw yesterday was all set to go , and then the pressure started mounting ... and then he decided to pull out , '' Preston said . Although he was expected to be confirmed , it was also expected that he 'd have to undergo a bruising confirmation hearing that could have led to negative headlines for Obama . As news broke of the withdrawal , some senators said they were sad to see Daschle step aside , but others said it was the right thing to do . `` I 'm in shock . I did n't know that . I do n't know what happened , '' said Sen. Dianne Feinstein , D-California . `` I talked to him ... the night before last , and he showed no signs of withdrawing . '' Feinstein praised Daschle as rare person who could get something like health care through the Senate and said she wishes he had not withdrawn . `` I have great faith in him . '' Sen. John Cornyn , R-Texas , said Daschle `` did a service to President Obama '' by stepping aside . `` I think it really would have looked bad for the Senate to close ranks around a fellow member and sort of reinforce the idea that they were going to protect a member as part of the good ol' boys club , '' he said . Daschle has a lengthy history with members of Congress . He represented South Dakota in the House of Representatives for four terms , and he served in the Senate for three terms . He was the Senate majority leader from June 2001 to January 2003 and served as the minority leader before losing his re-election bid in 2005 . Sen. John Ensign , R-Nevada , said Daschle `` saved the president from being embarrassed '' by withdrawing . Watch Republicans weigh in on the move '' Sen. Max Baucus , chairman of the Senate Finance Committee , said he was `` a little stunned '' by Daschle 's decision . `` I thought he was going to get confirmed . I thought -- he 's a good man , and I thought he 'd be confirmed . I 'm surprised , '' said Baucus , D-Montana . Sen. John Kerry , D-Massachusetts , insisted that Daschle had owned up to his mistakes . `` He 's made his decision , I respect his decision , and we go on from there , '' Kerry said . Daschle 's resignation came hours after Nancy Killefer 's withdrawal as Obama 's chief performance officer , a new post in the administration . Officials said privately the reason for Killefer 's withdrawal was unspecified tax issues . The much-touted post was designed to scrub the federal budget . CNN 's Lisa Desjardins , Candy Crowley and Kristi Keck contributed to this report .