It may happen because a nominee has lied about his or her background to Obama's team, or because something that was dismissed as minor turns out to be a big deal.
Whatever the reason, "These things are likely to pop up at any time — even though they are trying their darndest to make sure that doesn't happen," says George Mason University Professor James Pfiffner, another expert on transitions.
The key, then, is for Obama to be prepared for a nomination gone bad, and to know how to handle it deftly. He needs to know when to cut his losses, and when to stand and fight.
History tells Obama all he needs to know about the pitfalls of failing to check out nominees thoroughly and of letting a problem appointment fester.
Remember Linda Chavez? Probably not.
That's because President-elect Bush did the smart thing in 2001 when word surfaced that his choice for labor secretary had housed an illegal immigrant. Bush quickly cut Chavez loose, making clear he would not defend her. She withdrew her nomination just three days after the immigrant issue surfaced, and the story quickly died.
Contrast that with President Clinton's long, frustrating search for an attorney general in 1993.
First, he nominated Zoe Baird. When word leaked that she had hired illegal aliens as household workers and failed to pay their Social Security taxes, Clinton blamed a slipshod review process. "Nobody said anything to me about the taxes," he complained.
Next, he settled on federal judge Kimba Wood. Her nomination never went forward after the disclosure that she had hired an illegal immigrant as a baby sitter, even though she broke no laws and had paid the required Social Security taxes.
The drama dragged on for almost two months, casting a shadow over Clinton's inauguration: He'd first nominated Baird at a Christmas Eve news conference in 1992; it was Feb. 11 when he nominated Janet Reno.
A few months later, Clinton jettisoned the nomination of old friend Lani Guinier as an assistant attorney general after critics said her writings were too liberal. "I had not read her writings. In retrospect, I wish I had," Clinton said. That drama stretched out over five weeks, and left women and blacks outraged that Clinton had abandoned Guinier after letting her twist for so long.
When problems with a nomination emerge, "you can't allow it to linger and fester" as Clinton did, said Light. "It was horrible," he said, "and it cost him a great deal of political capital."
Obama appears to be treading carefully as he settles on his first Cabinet choices. His transition team has been quietly making inquiries on Capitol Hill to probe for any potential objections among lawmakers, and he's been requiring candidates to complete an extremely detailed questionnaire aimed at ferreting out any damaging information. Many of the earliest names to emerge — none formally announced yet — are prominent figures who've already survived public scrutiny, such as New York Sen. Hillary Rodham Clinton for secretary of state and former Senate Majority Leader Tom Daschle for health and human services secretary.
Martha Kumar, a presidential scholar at Towson University in Maryland, said it's especially important to get nominations right during a presidential transition, when people are watching most closely and making judgments about a new president's leadership.
"You're coming in with something of a clean slate, so you don't want to make a mistake," she said. "You have the public watching and you also have the public sympathy."
Historian Light said experience shows that the lure of a Cabinet appointment sometimes proves irresistible to people who should know better.
"The ambition to be a presidential appointee is so great that somebody's not going to tell the truth, no matter how hard you push the vetting process," said Light. "It happens all the time. There have been some recent nominees who just flat-out lied when asked whether there was anything about their personal or financial history that might embarrass the president."
Clinton was far from alone in running into problem nominations.
In January 1989, Tower seemed headed to confirmation despite reports of a drinking problem and womanizing. Then came fresh allegations about Tower that gave new life to the opposition. Bush still refused to back down, pushing the nomination all the way to a vote in the full Senate, which rejected Tower, 53-47, on March 9.
For Jimmy Carter, it was his choice of former Kennedy administration figure Ted Sorensen for CIA chief that turned sour. Sorensen withdrew his name on the eve of his Senate confirmation hearing, blaming "scurrilous and unfounded personal attacks."
Criticism had centered on Sorensen's past handling of classified materials, and his registration for noncombatant status with his draft board. (Among the senators who expressed reservations: Sen. Joe Biden, now the vice president-elect.)
Carter praised Sorensen's decision to withdraw as "characteristically generous and unselfish, designed to spare the administration and the country the effects of a divisive and emotional controversy."