CONCORD, N.H. — Three major Democratic candidates — Senators Clinton, Obama, and Edwards — claimed patches of territory here yesterday, beginning the furious 42-day home-stretch until the nation’s first presidential primary. A recent poll by a New Hampshire TV station, WMUR, showed that roughly half of the state’s Democrats were still undecided.

Buoyed by the endorsement of a prominent physician and wife of the state’s governor, Susan Lynch, Mrs. Clinton is vowing to campaign in the Granite State as much as possible between now and January 8.

Mrs. Clinton spoke briefly with reporters following her receipt of the endorsement of Susan Lynch at the historic Kimball-Jenkins estate. “There’s something very special about the New Hampshire primary. It means a lot to me personally because of my experience with it in back in ’92,” she said. “I’m going to be back here as often as I can. I take nothing for granted.”

During her scripted comments, Mrs. Clinton made an appeal to supporters for help at the event. “It is 43 days to the New Hampshire primary … and I need your help more than ever,” she said. Earlier, New Hampshire’s House speaker, Terie Norelli, urged attendees to participate in phone banks, talk to neighbors, and write letters to newspapers on Mrs. Clinton’s behalf. Such work constitutes the unglamorous field work that can make the difference in a small-state primary. Mrs. Clinton’s candidacy, in this regard, likely will receive a boost from Dr. Lynch’s endorsement, especially if it means that the doctor can bring some of her husband’s political supporters along with her — although Governor Lynch is officially neutral in the race.

After her speech, Mrs. Clinton ventured beyond the confines of her security detail to talk to an 87-year-old activist in a wheelchair, Mary Louise Hancock, who handed the senator a Susan B. Anthony medal. “I’ll give it back to you on election day,” Mrs. Clinton said. “That’s a great gift.”

The endorsement also involved policy. Dr. Lynch praised Mrs. Clinton’s health-care proposal for being “truly universal.” Mrs. Clinton added that her plan addressed both the uninsured and those who have insurance but are denied reimbursement.

Meanwhile, Mr. Obama campaigned in Littleton, and both New Hampshire and the rest of the country were abuzz as a result of his announcement that he would appear in the state with Oprah Winfrey on December 9. Mr. Edwards played on his outsider credentials at an event in Bow. In addition, Mrs. Clinton and Mr. Obama tussled over a Washington Post story reporting that the Illinois senator had distributed more than $180,000 from his political action committee to politicians in Iowa, New Hampshire, and South Carolina. The Clinton campaign released a statement asking if the contributions were made “to officials and entities in states holding nominating contests?” The Obama campaign, in turn, circulated statements from a well-known campaign finance attorney, Robert Bauer, and a campaign spokesman, William Burton, saying the charges were “meritless” and contrary to a vow of Mrs. Clinton’s not to attack other Democrats.