There is a widespread feeling among donors and some advisers, though, that a comeback this time may be improbable. Her advisers said internal polls showed a very tough race to win the Texas primary  a contest that no less than Mr. Clinton has said is a “must win.” And while advisers are drawing some hope from Mrs. Clinton’s indefatigable nature, some are burning out.

Morale is low. After 13 months of dawn-to-dark seven-day weeks, the staff is exhausted. Some have taken to going home early  9 p.m.  turning off their BlackBerrys, and polishing off bottles of wine, several senior staff members said.

Some advisers have been heard yelling at close friends and colleagues. In a much-reported incident, Mr. Penn and the campaign advertising chief, Mandy Grunwald, had a screaming match over strategy recently that prompted another senior aide, Guy Cecil, to leave the room. “I have work to do  you’re acting like kids,” Mr. Cecil said, according to three people in the room.

Others have taken several days off, despite it being crunch time. Some have grown depressed, be it over Mr. Obama’s momentum, the attacks on the campaign’s management from outside critics or their view that the news media has been much rougher on Mrs. Clinton than on Mr. Obama.

And some of her major fund-raisers have begun playing down their roles, asking reporters to refer to them simply as “donors,” to try to rein in their image as unfailingly loyal to the Clintons.

And yet, advisers say, the mood was even grimmer in early February, when the campaign was running out of money and the possibility of losing some major Feb. 5 primaries, like California and New Jersey, was unsettling Mrs. Clinton, of New York, and her aides. (She ended up winning those states.) The turbulence this time, some advisers say, has turned into greater focus and determination toward clear targets: the Ohio and Texas primaries.

In interviews with 15 aides and advisers to Mrs. Clinton, not a single one expressed any regrets that they were not working for Mr. Obama. Indeed, some aides said they were baffled that a candidate who had been in the United States Senate for only three years and was a state lawmaker in Illinois before that was now outpacing a seasoned figure like Mrs. Clinton. And to a person, these aides and advisers praised Mrs. Clinton and said that she had been a better candidate than her campaign strategy and operation reflected.