Democratic Presidential hopeful John Edwards listens to his wife, Elizabeth, speak about her recurrence of cancer during a news conference Thursday in Chapel Hill, N.C. Edwards will continue his campaign for the presidency.

Washington ? Democrat John Edwards said Thursday that his presidential campaign “goes on strongly” in the face of a repeat cancer diagnosis for his wife, Elizabeth, a somber development that thrust his White House bid into uncharted territory.

The couple revealed that Elizabeth Edwards’ breast cancer had spread to her bone during a news conference designed to reassure the public about the prognosis for her health and his candidacy.

“The bottom line is, her cancer is back,” said John Edwards, the 2004 vice presidential nominee and former senator, at a news conference in their hometown of Chapel Hill, N.C. “We are very optimistic about this, because having been through some struggles together in the past, we know that the key is to keep your head up and keep moving and be strong.”

The Edwardses suffered through the death of their teenage son, Wade, in 1996 and Mrs. Edwards’ breast cancer diagnosis the day after John Kerry and John Edwards lost the 2004 election. She was treated with surgery and several months of radiation and chemotherapy.

The recurrence of the cancer presents a setback for the couple, both personally and politically.

“Getting these results was not a good day for us,” John Edwards said.

Elizabeth Edwards’ illness and treatment are certain to affect her husband’s campaign schedule and may raise questions about the viability of his campaign, especially among financial donors wondering whether he will be in for the long haul. The first fundraising deadline is fast approaching on March 31.

Edwards has been considered among the top-tier candidates although he trails front-runners Hillary Rodham Clinton and Barack Obama in public opinion polls. His forceful opposition to the Iraq war – and oft-repeated apology for his 2002 vote for it – as well as his plans on universal health care have improved his standing among the party’s liberal base.

Both Edwardses said the cancer was treatable and that they would stick with their plans to campaign vigorously for the nomination.

“The campaign goes on. The campaign goes on strongly,” said Edwards, who argued, “other than sitting around feeling sorry for ourselves, there was no reason to stop.”

Other candidates have faced cancer in their families and have not let it slow their campaign. Chicago Mayor Richard M. Daley ran for re-election this year despite his wife’s diagnosis of metastatic breast cancer in 2002.

Republican presidential candidate John McCain has had repeat occurrences of skin cancer. McCain rival Rudy Giuliani is a prostate cancer survivor, as was 1996 Republican nominee Kansan Bob Dole and 2004 Democratic nominee John Kerry.

Democrat Paul Tsongas made his survival from cancer an issue in his 1992 campaign for the Democratic nomination. He lost the primary to Bill Clinton. Tsongas’ cancer later returned and he died three years later.

The recurrence was discovered after Mrs. Edwards broke a left rib, likely moving a chest, and had X-rays that also found something suspicious on the right side.

Elizabeth Edwards’ doctor called her in for more testing, and her husband cut short a campaign visit to Iowa to accompany her to the hospital Wednesday. A biopsy confirmed that the cancer had returned, and the Edwardses are awaiting further testing to see if the cancer may have spread to her liver.

“There were times yesterday that we thought it might be a lot worse than it is, and we wouldn’t be having the same conference we’re having right now with the same hopeful tone,” Elizabeth Edwards said.