WASHINGTON -- Buoyed by polls showing tight races in today's key primaries, Hillary Clinton is preparing to press ahead with her presidential campaign, even if she wins only one big state.
Clinton trails Barack Obama for the Democratic nomination, and she has no realistic chance of erasing his lead in delegates allocated through primary and caucus contests, including today in Ohio, Texas, Vermont and Rhode Island.
But officials of both campaigns were resetting expectations yesterday as they prepared for an outcome that once seemed unlikely: a Clinton revival after a losing streak of 11 straight contests since Super Tuesday.
"I'm just getting warmed up," Clinton said yesterday. Late polling showed her with a slight edge in Ohio, while Texas was a statistical dead heat.
Clinton told reporters aboard her campaign plane that today's primaries are "going to be a very significant message to the country, and then we move on to Pennsylvania and the states coming up." Pennsylvania, the next big primary contest and a state similar to Ohio, holds its election seven weeks from today, on April 22.
Mark Penn, the chief Clinton campaign strategist, predicted that "the momentum of Senator Obama will be significantly blunted" in today's primaries.
Clinton's communications director, Howard Wolfson, said during the same conference call that if Clinton holds off Obama, it would be a sign that Democratic voters have serious doubts about him and that "a serious case of buyer's remorse is setting in" about making him the nominee.
Obama victories in Ohio and Texas would almost certainly end the Democratic contest. For some time, Clinton strategists had described both states as must-win for her.
More recently, though, they've suggested that winning Ohio alone would be enough to keep her in the race.
Neutral Democrats and Clinton supporters say she's likely to stay in the race unless she loses both Ohio and Texas.
"This feels to me like a campaign that's going forward," said a top adviser to the Clinton campaign, who spoke on condition he not be identified.
This adviser laughed at the idea, being advanced by some in the Obama camp, that senior Democrats - such as House Speaker Nancy Pelosi and former Vice President Al Gore - would force Clinton to abandon her run if she doesn't win both big states.
"It's the Democratic Party, come on. Chaos is in our DNA," he said, adding that there was no recent history of party officials persuading a presidential contender to quit.
Chris Lehane, a former Clinton White House aide and Gore's 2000 presidential campaign spokesman, who is not involved this year, said he learned a long time ago to never count out Hillary Clinton.
For a presidential candidate, "it usually comes down to whether you have the fuel to keep going, which in campaigns is money," and Clinton has the financial capacity, he said.
Clinton will also feel she has an obligation to her donors and supporters to continue as long as she can see a path to the nomination, he said.
That path depends on convincing hundreds of superdelegates - party officials who hold the key to the nomination - that she is the strongest candidate against John McCain, the likely Republican nominee.
A victory in Ohio, perhaps the most important swing state in the general election this fall, would be essential to that argument.
Obama's campaign, flush with cash after raising more than $50 million last month, has gone all out to finish Clinton off.
Last week, for example, Obama gave college students round-trip airplane tickets from New England to Texas for several days of work there as campaign volunteers.
Facing possible setbacks in Ohio or Texas, or both, the Obama campaign is trying to refocus attention on the delegate count.
For weeks, his top aides have maintained that one reason Obama should be the nominee is that he won more states than Clinton during the primary season.
But in something of a shift, Obama campaign manager David Plouffe said during a conference call that "it's less about the states than it is about the delegates."
Obama's side argues that the candidate who wins the most delegates in the primaries and caucuses should be the nominee.
Any effort by the Clinton campaign to win the nomination in an "alternative and underhanded" manner would amount to an effort to "overturn the will" of Democratic voters, said Plouffe.
However, neither candidate is expected to win the 2,025 delegates needed for the nomination in the primaries alone. Obama has won more delegates in the primaries and has been steadily cutting Clinton's advantage among superdelegates.
Plouffe, the Obama campaign manager, in a memo entitled "The Real Meaning of March Fourth," contended that even with "narrow popular vote wins in Texas and Ohio," Clinton "will be facing almost impossible odds to reverse the delegate math."
According to Obama's calculations, Clinton would need to win at least 62 percent of the remaining pledged delegates after today to catch Obama. Clinton's camp no longer contends that she will overtake him on the basis of primaries and caucuses alone.
But if she survives today's contests and wins Pennsylvania, the race will continue well into the summer and, quite possibly, to the national convention in Denver at the end of August.
The prospect of an internal fight that lasts another six months is chilling to some Democratic officials.
Their fear: that the eventual nominee would emerge so battered that McCain would win in November.
Over the weekend, New Mexico Gov. Bill Richardson, who unsuccessfully sought the nomination, began the drumbeat for a swift end to the race.
He said that, after today, the candidate who has won the most delegates in the primaries should be the nominee - a tacit endorsement of Obama.
But with roughly 350 superdelegates yet to commit publicly to either candidate, and Obama leading by only about 110 delegates, the chances of a rapid conclusion to the campaign may disappear if today's primary voters save Clinton's candidacy.