The key to Senator Clinton’s winning the Democratic nomination is expected to come from an overwhelming primary victory February 5 in her home state, New York, with its 281 delegate votes, and her popularity among those who work in New York City but live in the adjoining states of New Jersey, with 127 votes, and Connecticut, with 60 votes.

The tristate area, with its 468 votes, offers an even bigger prize than the plum state of California, which has 441 delegate votes and also votes on February 5, and where Mrs. Clinton’s team expects her to do well.

It is a paradox of the 2008 presidential race that Mrs. Clinton is expected to succeed by following the big state strategy that her arch rival Mayor Giuliani charted as his best chance of winning the Republican nomination.

Mr. Giuliani may, like Mrs. Clinton, also win a single but significant primary, in Florida on January 29, the week before Super Tuesday, when 23 states select their preferred candidate.

Mrs. Clinton’s minders are deliberately underplaying her chances of winning another state before Super Tuesday.

She faces a tough contest on January 19 in Nevada, where yesterday the largest trade union, the Culinary Workers Union and its 60,000 members, decided to throw its organizational power behind Senator Obama, and in South Carolina, where the Illinois senator is expected to do well with African-Americans, who make up about 45% of Democratic voters.

However, the New Hampshire turnaround in Mrs. Clinton’s fortunes is thought significant enough to have stopped the momentum Mr. Obama gained by winning Iowa, allowing her to weather a possible resurgent Obama campaign heading into the big state contests.

Mrs. Clinton’s advisers say they do not believe the Obama threat has completely subsided, and they are prepared for her not to win but to achieve respectable results in Nevada and South Carolina.

Central to the calculation that Mrs. Clinton will be unstoppable come the morning of February 6 is her strength in New York State and its neighbors New Jersey and Connecticut.

She is expected to do well in all three states, which distribute delegate votes proportionate to the number of votes won by candidates.

The decision by Mrs. Clinton to enter the 2000 Senate contest in New York, replacing the veteran liberal Senator Moynihan in the Democratic seat, may prove to be the key to her success in winning the her party’s nomination this year.

The vast population surrounding New York City gives any popular hometown candidate an enormous advantage over rivals. Mr. Obama’s home state of Illinois, which also votes February 5, boasts only 185 delegate votes.

Although the most recent survey of primary polling intentions in New York was taken three weeks ago, before the rollercoaster ride of Iowa and New Hampshire, Mrs. Clinton’s dominance of the political machine in her home state suggests that Mr. Obama stands little chance of catching up with her, short of a disastrous gaffe by her or her husband.

Mrs. Clinton is overwhelmingly popular among registered Democrats in New York State, a Quinnipiac survey of primary voting intentions by New York Democrats on December 17 found. She polled 55%, 38% more than Mr. Obama, with John Edwards at 7%.

A poll of New York Democrats for Datamar the previous week gave Mrs. Clinton 44.5% support, with Mr. Obama at 10.8% and Mr. Edwards 13%.

The poll estimated the African-American proportion of likely primary voters in New York to be 4.8%.

The latest polling in California also bodes well for Mrs. Clinton. She leads the Democratic field with 36%, according to a survey by Field Research on December 19. Mr. Obama scored 22% and Mr. Edwards 13%, with 20% undecided.

Most tellingly, in light of the recent turnaround in New Hampshire, 52% of likely voters in the primary thought Mrs. Clinton the candidate with the best chance of winning the general election in November, compared to 18% who think Mr. Obama could win.

If Mr. Edwards were to drop out of the California race, which he denies is likely, the poll suggests the former trial lawyer’s support would split nearly two to one in favor of Mr. Obama, with 40% giving Mr. Obama as their second choice, 24% naming Mrs. Clinton, and 11% favoring Governor Richardson of New Mexico.

With Mr. Richardson’s withdrawal from the California race, his departure is likely to benefit Mrs. Clinton, who, the poll shows, leads Mr. Obama by 20% among Hispanic Democrats.