BOSTON -- For much of his life, Sen. Edward M. Kennedy has taken on the role of caregiver, watching over his extended family after tragedies, pushing for sweeping health care, retirement and education legislation, answering the phone to field the concerns of a constituent.

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Now he is the one in need after being diagnosed with a cancerous brain tumor. Some experts gave the liberal lion less than a year to live.

Doctors discovered the tumor after the 76-year-old senator and sole surviving son of America's most storied political family suffered a seizure over the weekend. The diagnosis cast a pall over Capitol Hill, where the Massachusetts Democrat has served since 1962, and came as a shock to a family all too accustomed to sudden, calamitous news.

In an e-mail sent to friends, Kennedy's wife, Vicki, acknowledged the family had been "pitched a real curveball," but said "this is only the first inning." She said the family was consulting with experts and seeking multiple opinions.

Kennedy's doctors said tests conducted after Kennedy suffered a seizure this weekend show a tumor in his left parietal lobe. His treatment will be decided after more tests but the usual course includes combinations of radiation and chemotherapy.

Political partisanship has been put aside as word spreads that Kennedy is suffering.

Both Democratic presidential candidates paused during the day to express best wishes to Kennedy.

During a speech in Iowa Tuesday night Sen. Barack Obama said, "So many of us here have benefited in some way or another because of the battles he's waged, and some of us are here because of them."

Sen. Hillary Rodham Clinton sent her regards to Kennedy as well. "As a lifelong champion for social justice and equality, his work has made the path easier for me, for Senator Obama and for countless others. He's been with us for our fights and we're now with him in his," Clinton said.

The man either Obama and Clinton will face in the general election, Sen. John McCain, R-Ariz., said his prayers are with the Kennedy family.

"I have said on numerous occasions, I have described Ted Kennedy as the last lion in the Senate, and I have held that view because he remains the single most effective member of the Senate if you want to get results," McCain said.

Earlier in May, Kennedy teamed up with cyclist and cancer survivor Lance Armstrong in a Senate hearing to draw attention for a new push in what he called a "war on cancer."

Calling the seven-time Tour de France winner "a true champion of will and determination," Kennedy said the Texan "has changed the way people see cancer patients."

He also lavished praise on two other invited speakers, breast cancer survivor Elizabeth Edwards, wife of former Sen. John Edwards, and AOL founder Steve Case, who has spearheaded a nonprofit group's anti-cancer work.

Kennedy announced legislation he intended to file soon to encourage more coordination of cancer research, prevention and treatment. The legislation also would give more money to the National Cancer Institute and other public research agencies.