The White House both underscored the magnitude of the problem and tried to downplay it in the space of seven words. “Nobody’s perfect,” said press secretary Robert Gibbs. “It was a serious mistake. …”

Nobody was predicting defeat for Daschle’s nomination as secretary of health and human services, but it was proving an unsavory pill to swallow for senators who only last week confirmed Timothy Geithner as treasury secretary despite his separate tax-payment problems. It’s an issue that strikes a nerve among lawmakers’ constituents who are struggling with their own serious money problems.

On the bright side for Daschle, he got warm words of support from the chairman of the Senate Finance Committee, the panel that will have the first say on his fate. Daschle has been “an invaluable and expert partner” in efforts toward health care reform, said Democrat Max Baucus of Montana — an especially important endorsement since the two men have had tussles in the past over Baucus’ handling of GOP tax-cut proposals, Medicare changes and other issues.

A number of other Democrats on the committee also voiced their support. John Kerry of Massachusetts said that “there is a completely understandable, absolutely acceptable and rational explanation for what happened here.”

Republicans weren’t so quick to get in line.

Going into a private meeting between Daschle and committee members late Monday, Iowa Sen. Chuck Grassley, top Republican on the Finance panel, was asked if he supported the nomination. He responded, “Ask me after the hearing a week from tomorrow,” a reference to Daschle’s public confirmation hearing.

After the meeting, which lasted a little more than hour, Daschle apologized anew.

“It was completely inadvertent, but that’s no excuse,” he said. “I apologize to President Obama, to my colleagues and to the American people.”

Daschle, the former Senate Democratic leader, expressed his remorse earlier in a letter to the Finance Committee, saying he was “deeply embarrassed and disappointed” about what he said was an unintentional failure to pay taxes that he owed. He recently filed amended returns for 2005-07 to report $128,203 in back taxes and $11,964 in interest.

Obama, asked at the White House whether he was standing by his nomination, answered, “Absolutely.” He did not elaborate.

Vice President Joe Biden, a former longtime senator, was making calls to Capitol Hill trying to cement support.

In his letter, released Monday, Daschle sought to explain how he overlooked taxes on income for consulting work and the use of a car service. He also deducted more in charitable contributions than he should have.

White House spokesman Gibbs noted Daschle’s long tenure as a senator from South Dakota and said it would be up to the Senate to weigh a “serious, but corrected mistake against that three-decade career in public service.”

“We still think he’s the best person to do health care reform and shepherd a very complicated process through Congress to achieve savings and cut costs for the American people,” Gibbs said. The White House also had suggested Geithner was indispensable for the national economic revival in arguing for his confirmation despite tax problems.

Daschle was an early supporter of Obama’s presidential bid, and several of Daschle’s former Capitol Hill staffers went to work for Obama after the senator lost his re-election bid in 2004.

He filed the amended tax returns after Obama announced he intended to nominate him as secretary of health and human services.

“I disclosed this information to the committee voluntarily and paid the taxes and any interest owed promptly,” Daschle wrote. “My mistakes were unintentional.”

On another matter, a financial disclosure form Daschle filed about a week ago showed that he made more than $200,000 in the past two years speaking to members of the health care industry that Obama wants him to reform.

The speaking fees were just a portion of the more than $5.2 million the former senator earned over the past two years as he advised health insurers and hospitals and worked in other industries such as energy and telecommunications, according to a financial statement filed with the Office of Government Ethics.

Among the health care interest groups paying Daschle for speeches were America’s Health Insurance Plans, $40,000 for two speeches; CSL Behring, $30,000; the National Association of Boards of Pharmacy, $16,000, and the Principal Life Insurance Co., $15,000.

Associated Press Writers Julie Pace and Steven R. Hurst contributed to this story.