The Senate slowed to an emotional standstill Tuesday afternoon as Senators grappled with the sobering news that one of the chamber’s iconic figures, Sen. Edward Kennedy (D-Mass.), had been diagnosed with a life-threatening brain tumor.

Reactions were heartfelt and far-reaching, coming from Democrats and Republicans. Some Senators teared up, others found themselves at a loss for words, and all said they were praying for Kennedy’s full recovery in his fight against cancer.

With his eyes welling, Sen. Chris Dodd (D-Conn.), Kennedy’s closest Senate confidant, struggled to speak before reporters. He said he was confident his lifetime friend would win the battle, calling the 76-year-old a “strong guy with a great heart.”

Sen. Patrick Leahy (D-Vt.), who similarly has served with Kennedy for decades, called Tuesday “one of the worst days I’ve had in 34 years. There’s not much more I can say.”

Ninety-year-old Sen. Robert Byrd (D-W.Va.) sobbed openly on the Senate floor: “Ted, Ted, my dear friend, I love you and I miss you. … Thank God for you, Ted. Thank God for you.”

Kennedy’s cancer was revealed in the afternoon by his doctors at Massachusetts General Hospital in Boston, where the Senator has remained since Saturday morning. Kennedy was airlifted there after suffering a seizure at his family’s compound in Hyannis Port. Initial reports had suggested that Kennedy may have experienced a stroke, but later those were dismissed and a brighter outlook was projected.

In Tuesday’s statement, Kennedy’s doctors gave a frank assessment. “Preliminary results from a biopsy of the brain identified the cause of the seizure as a malignant glioma in the left parietal lobe,” they said. Malignant glioma is the most common type of primary brain tumor, and according to the National Cancer Institute, the prognosis can be very poor with survival rates ranging less than a year to several years.

“The usual course of treatment includes combinations of various forms of radiation and chemotherapy,” Kennedy’s doctors said. “Decisions regarding the best course of treatment for Senator Kennedy will be determined after further testing and analysis. Senator Kennedy will remain at Massachusetts General Hospital for the next couple of days according to routine protocol. He remains in good spirits and full of energy.”

Kennedy has had health problems in recent years. Last October, he underwent surgery to open a blocked artery in his neck. The surgery was performed to lessen the risk of a stroke.

Senate Majority Leader Harry Reid (D-Nev.), who delivered Kennedy’s cancer diagnosis to Democratic Senators during their weekly policy luncheon, called his colleague “a marvel of public service” who is “truly an American icon.” Like most Senators, Reid used the term “fighter” to describe Kennedy and said that just like his other battles throughout his nine terms, Reid was confident that Kennedy “will rise to this as well.”

Reid, who spoke to Kennedy’s wife, Vicky, on Tuesday, said Kennedy “knows how we feel about him without our even telling him. We are confident in his recovery.”

Kennedy was first elected to the Senate in 1962 and has been a defining figure in Democratic and American politics for decades. The brother of the late President John F. Kennedy and Sen. Robert F. Kennedy, he has championed many of the party’s landmark legislative fights, including civil rights, education, labor protections and health care benefits.

Those efforts, coupled with his roaring debate style, earned him the nickname “the liberal lion.” Kennedy ran unsuccessfully for president in 1980, only to return to the Senate, where he has made his mark as one of the chamber’s most revered and influential.

It remained unclear when Kennedy, the chairman of the Health, Education, Labor and Pensions Committee, would return to the Senate. What seemed certain, however, was that Kennedy would not be back at work this week as Senators work through a politically charged supplemental spending bill for Iraq and prepare to adjourn for the weeklong Memorial Day recess.

Senators in both parties acknowledged the emotional toll Kennedy’s diagnosis was having on the chamber as it tries to wrap up business for the week. It appeared unlikely that Reid would defer the Senate’s work altogether, but Democrats seemed disinclined to press ahead with much of the business at hand on Tuesday.

“I’ll tell you what: There’s a big supplemental coming onto the floor and our side is very depressed, and it’s hard,” Sen. Dianne Feinstein (D-Calif.) acknowledged. “I do think we need some time to come to grips with some of this.”

Still, Senate Democrats said they would make sure none of Kennedy’s work goes undone. For example, on Tuesday, Leahy and Sen. Sherrod Brown (D-Ohio) chaired hearings on Kennedy’s behalf.

“I think everybody’s going to jump in and help during Sen. Kennedy’s absence because everyone knows he wants the work of the Senate to continue,” Sen. Ben Nelson (D-Neb.) said.

Democrats have had to rise to the challenge before, beginning last year when Sen. Tim Johnson (D-S.D.) was stricken with a brain aneurysm that sidelined him for months. Johnson, who is back at work full time, ceded his committee duties to some of his colleagues in the interim, including his chairmanship of the Appropriations Subcommittee on Military Construction, Veterans Affairs and Related Agencies.

Republican Senators have wrestled with their share of health issues during this Congress as well. Sen. Arlen Specter (Pa.) was recently diagnosed with a recurrence of a form of Hodgkin’s disease, and Sen. Craig Thomas (Wyo.) died last summer of complications stemming from leukemia.

The somberness of Senate Democrats over Kennedy was palpable, and similarly, Senate Republicans — many of whom also have known the senior Massachusetts Senator for years — were emotional. Republicans held a moment of silence and said a prayer for Kennedy during their private luncheon after hearing the news.

Sen. Lindsey Graham (R-S.C.), who worked closely with Kennedy during last year’s immigration reform negotiations, said that while “he doesn’t agree with Sen. Kennedy a lot,” he “admires him a lot and considers him a friend.”

“I hope for the best — he’s a tough guy,” Graham said. “My money’s on Ted.”

Similarly, one of Kennedy’s closest Republican friends, Sen. Orrin Hatch (Utah), said he was “heartbroken” about the news of a man he considers his “brother.”

“I still have faith with modern radiology that we may be able to do some things here,” Hatch said.