The drumbeat urging Senator Clinton to concede defeat is growing. Mrs. Clinton is damaging the Democratic Party. She is making Senator Obama’s eventual task of winning the general election more difficult, while granting Senator McCain time to cozy up to the voters. She is putting herself, and her ambition, and the ambition of her husband ahead of the common good. She cannot win, so why is she still in the race?

This chorus of disapproval is speaking up at a strange time. There are still three weeks before the Democrats vote in Pennsylvania and, according to RealClearPolitics, polls suggest she is more than 10 points ahead. The state is perfect territory for her, white, older blue collar workers with large numbers of working women, the sort of old Democratic heartland that is too down to earth to be much impressed by soaring speeches and the promise of “new politics.”

So why do her opponents think she will crumble simply because they have asked her to? In politics it is generally best not to call for something unless it is already a certainty. No one believes Mrs. Clinton will stand down until she is roundly and unambiguously defeated, whether in Pennsylvania on April 22, which looks unlikely, or in North Carolina and Indiana, on May 6. The chances remain that, short of a special superdelegate convention in June, we are headed to a bruising battle on the conference floor in Denver in August.

Those who are enjoying Mrs. Clinton’s discomfort and who express indignation that by staying in the race she is, somehow, not playing the game might remember a previous presidential candidate who would not give up in similar circumstances. In 1976, Ronald Reagan, amid calls of treachery, ran against a Republican president, Gerald Ford, and he took his fight all the way to a divided convention in Kansas City.

Reagan lost to Ford in New Hampshire, then Florida. He even lost his own boyhood state of Illinois by nearly 20 points. His campaign ran out of funds and, before eventually winning in North Carolina, his campaign manager urged him to abandon the race. The question reporters most often asked Reagan was, “When are you going to drop out?”

Despite losing more states than he won, and falling short in delegates by a mere 137 delegates — according to RealClearPolitics, without Michigan and Florida Mrs. Clinton is currently 136 delegates behind Mr. Obama — Reagan insisted that he had every right to take his campaign to the finishing line. The convention was a torrid affair where, no sooner was Ford declared the narrow victor than Republicans of every hue began experiencing buyers’ remorse.

Like Mrs. Clinton, Reagan dearly liked to win and he was not prepared to allow the convention to become a coronation. Ford’s campaign staff had exiled the former California governor to a glass booth high up in the convention hall so that he and Nancy, who held court there, would not detract from Ford’s annunciation.

However, keeping Reagan cooped up was a profound error. When Ford, after a halting, plodding acceptance speech, beckoned to Reagan to come down to the platform and join the celebrations, Reagan sat with his back to the action and appeared to snub him. And when Reagan was finally lured to share the platform with Ford, the beaming former actor, reveling in his late entrance, launched into a speech that demonstrated the best man had indeed just lost.

Mrs. Clinton has been running for president for years. Notwithstanding the absence of snipers at Tuzla Air Base, she was a more politically energetic First Lady than any since Eleanor Roosevelt, or even Edith Bolling Galt, the second Mrs. Woodrow Wilson, who ran the government single handedly after Wilson’s incapacitating stroke.

Mrs. Clinton has paid a high personal price to fulfill her goal. She had to swallow her pride when her husband humiliated her. She has become the target of acerbic abuse from her political opponents and derision from much of the press, who greet her every new setback with the glee of schoolboys watching their headmistress slip and slide in the snow.

But whatever she may feel in private, in public she remains steadfast and resolute. She suffers no defeats, only setbacks. Like Reagan, she has no intention of giving up. She continues to smile through her adversities and keep her options open, all qualities we might expect from anyone with a claim to becoming our president and commander in chief.

And if not this year, Mrs. Clinton has her sights set on 2012. Despite those who prefer to believe that Obama-mania is evidence of an end to the nation’s deep political divisions and that the chilling videos of the Reverend Jeremiah Wright’s unpatriotic rantings have been safely wiped, Mr. McCain remains the favorite to win in November.

In 2012, Mr. McCain will be 76. Mrs. Clinton will be 65 that year and 69 in 2016. So, even her defeat in Denver will not mark the end of the Clinton saga. Only if Mr. Obama wins in November and can succeed in making good on his promise to unite the country within four years will Mrs. Clinton be deterred from resuming her White House quest in 2012.

Mr. Wapshott is the author of “Ronald Reagan and Margaret Thatcher: A Political Marriage,” published by Sentinel.