Even while battling the brain cancer that would kill him, Sen. Edward M. Kennedy chalked up legislative successes this year.

The economic stimulus law included provisions to expand the use of electronic medical records, long a Kennedy priority. Congress cleared an expansion of the Children's Health Insurance Program, which Kennedy, D-Mass., helped create in 1997. Congress passed a law named for Kennedy that would expand national service programs, such as AmeriCorps. And he lived long enough to see a law signed that would authorize the Food and Drug Administration to regulate tobacco products, another long-sought goal.

Senate More Partisan Without Kennedy
Kennedy died Tuesday night, without getting to vote on what he called the cause of his life -- an overhaul of the nation's health system, aimed at providing every American access to insurance coverage.

Congress must move on without him on health care and a number of other issues that have become indelibly tied to Kennedy: among them, legislation that would make it easier for unions to organize workplaces, and an overhaul of the immigration system to provide legal status to millions of workers living in the country illegally.

In his absence, Kennedy's colleagues and former aides say, debate is likely to be more strident, partisanship more pronounced, compromise less attainable and success less certain.

"The loss is tremendous," said Sen. Christopher J. Dodd, D-Conn., one of Kennedy's best friends in and out of the Senate. "Obviously, his presence, because he was a quintessential legislator. He understood the Senate as well as anybody ever has."

In part, that was thanks to his longevity in the chamber: Kennedy, first elected in 1962, served longer than all but two other senators. But friends and colleagues say Kennedy had an uncanny knack for timing -- especially for knowing when and with whom he should strike the legislative compromises for which he was known. Through his celebrity status, Kennedy commanded a deep and loyal following among liberal interest groups and a healthy respect among conservative groups. He was masterful at building relationships with his colleagues, he was smart, and former aides say that his work ethic was underrated.

"Even when he was a man in his 70s, he would be scheduled from morning till evening, and then he'd take a bulging bag of memos home that he'd read in the evening," said David Nexon, Kennedy's former longtime health policy director, now a senior vice president for the Advanced Medical Technology Association. Aides spent much of their days "rushing to make bag," as they called it, said another former aide, Jane Oates, now an assistant secretary at the Department of Labor.

"Every morning by 10:00 you had everything you had delivered to him the night before with notes, and comments, and details," she said.

Kennedy was a formidable opponent in floor debate, in part because he often read legislation himself, even when the bills were not his own.

"Sen. Kennedy would have us annotate the bill, and then he would read it before the debate." Nexon said. "He would typically know more about what was in the bill than the sponsor would."

Kennedy's Human Touch
But his true legislative gifts are intangible and difficult to quantify.

Stories of Kennedy's small displays of generosity are legion -- a note, or perhaps a card or flowers, sent to a colleague in the event of a birthday, or a birth in the family, or a tragedy.

The gestures not only helped win Kennedy friends in both parties, but also political allies.

"He would ask his colleagues, whether it was on the floor -- he would care to ask them, 'How are you doing, what's going on in your life?'" said Marc Schloss, an aide to Kennedy from 2000 to 2003 who is now director of federal government relations for the National Association of Chain Drug Stores. "He would come to me and say, You know, it turns out that Senator so-and-so's daughter is having surgery; we should send her flowers."

Some Republican senators -- notably Orrin G. Hatch of Utah, a close Kennedy friend and occasional legislative partner -- say that they think Kennedy already would have struck a bipartisan bargain on a health overhaul. (Hatch co-wrote a song in tribute to Kennedy and posted it on YouTube Wednesday.) The health effort instead has become more contentious with every passing month, and Senate Republican leaders now say they don't expect any member of their caucus will support the legislation.

Some of those close to Kennedy dismiss such talk. Republicans, said one senior Democratic leadership aide, are "trying to sell the process short when they say things like that."

"The fact is, Sen. Kennedy knew better than anyone else that it's better to take a half a loaf and continue to fight in the future than to get nothing at all," the aide said. "But the way the Republican leadership is operating, they don't want to give up even a quarter of a loaf."

Yet others, including Nexon and Dennis Rivera, health policy director for the Service Employees International Union, believe that the health bill would be further along had Kennedy been healthy enough to lead debate on the measure.

"He had the standing to speak to folks on the Republican side of the Senate," Rivera said. "We are missing Teddy; if Teddy was here, we would have moved this on a faster pace."

When Kennedy decided to move to the center on any issue, other members on both the right and left often found themselves with the political cover to follow him.

"It's sort of hard for a Democrat to be to the left of Sen. Kennedy," Nexon said. "The moderates had a tough time not going along too, because it was hard for them to be to the right of an Orrin Hatch or a John McCain or someone like that. Other senators don't have that kind of following in the country, in the sense that he speaks to liberals everywhere."

Dodd and others said they are sure that Congress will clear a health overhaul in Kennedy's absence. Issues with less momentum, however, may face more difficulty.

A Vote Short of 60
In practical terms, Senate Democrats are now another vote shy of the 60 they need to invoke cloture on a bill -- opposed by all Republicans -- that would make it easier for unions to organize.

Labor unions, which consider the bill a top priority, have lost one of their strongest spokesmen for the highly controversial measure. Rivera said he is confident Congress will nonetheless pass the bill, known informally as "card check."

An immigration overhaul, another Kennedy passion, also takes a hit with his death. Kennedy, descended from Irish immigrants, was a legendary supporter for immigrants and -- as with all his issues -- a strong spokesman for their cause.

"Nobody could speak with that clarity of both personal history and vision for our nation," said Ali Noorani, executive director of the National Immigration Forum, a group that advocates for an overhaul that would allow illegal immigrants a route to citizenship.

And yet Noorani is confident that Kennedy's work on the issue will outlast his death.

"If anything, the groundwork that he has laid makes passage of immigration reform in this session all that much easier," he said. Democrats hope that proves to be true on all of Kennedy's causes.

"Kennedy," Oates said, "would say that every obstacle is an opportunity."