ABC News’ Rick Klein reports: The White House announced today that Tom Daschle has just withdrawn his nomination to become secretary of Health and Human Services (HHS) and that President Obama has “reluctantly” accepted his decision. "To be chosen by President Obama to run the Department of Health and Human Services and to lead the reform of America’s health-care system is one of the signal honors of an improbable career," Daschle said in a statement. "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." This is a devastating blow to the new administration. Daschle is and has been one of the president’s closest allies, and Obama said Monday that he was “absolutely” sticking with him as his choice at HHS. He would have overseen a vast portfolio of health-care issues and agencies, including, of course, the signature issue of health-care reform and expansion. And this marks the third top official whose nomination has been withdrawn because of unanticipated problems involving vetting their histories — a statement on the Obama operation’s apparent haste in getting top posts filled. The setbacks are likely to embolden Republican opposition to Obama and his agenda — at a time where he can least afford it, as he struggles to get his stimulus plan through Congress.