When Edward Kennedy died in August, the country lost one of its most able lawmakers, a liberal who could cross the aisle on issues ranging from education to immigration. For Massachusetts, the loss was more visceral. During nearly 47 years in the Senate, Kennedy used his seniority, his family name, and his own persuasive skills to become the state’s best advocate, ensuring that Massachusetts received its share of federal funds and that its interests were never trampled by congressional or bureaucratic decisions.

“Ted Kennedy is irreplaceable,” says his successor as the state’s senior senator, John Kerry. “Lord knows I feel his loss every time I’m on the Senate floor or in the cloakroom. I look around and it’s still hard to believe he’s not there, but one of the gifts he gave us was his example and his teaching.”

If Kennedy was the Senate’s liberal lion, a dominant player in shaping legislation and in securing benefits for his home state, Kerry was always a loyal member of the pride, doing his part for the liberal cause behind the scenes. Now, though, Kerry is trying to step into a bigger role, both as the leading Senate voice on the Afghan war — from his new perch as chairman of the Senate Foreign Relations Committee — and on global warming. He is one of the lead sponsors of legislation to cap carbon emissions, which figures to dominate 2010 in the same way health care dominated 2009.

Kerry is also showing he is an independent thinker, especially in the area of foreign affairs, where he’s crossed President Barack Obama both in raising questions about the US military presence in Afghanistan and in moving legislation through his Foreign Relations Committee to overhaul the process by which the United States gives out foreign aid. (Obama would prefer to address the foreign aid issue without a congressional mandate.)

“I think Senator Kerry is rising to the occasion,” says colleague James McGovern, who has represented Worcester in the House since 1997. “He’s our new senior senator and he’s been out front on climate change and Afghanistan. He’s clearly taking on more responsibilities, and I’m glad to see it.”

Kerry was often overshadowed by Kennedy during the quarter century in which they overlapped in the Senate. And during his early re-election campaigns, Kerry was often criticized by opponents for the dearth of laws that bear his name, a charge that George W. Bush milked even in 2004, when Kerry was the Democratic Party’s nominee for president. So the new senior senator is understandably reluctant to discuss the prospect of filling Kennedy’s shoes. He says he’s “learned over the years not to get hung up on your role or your place in the scheme of things.”

David Leiter, a former Kerry chief of staff who is now a lobbyist in Washington, says his old boss isn’t changing his leadership style but is getting more scrutiny in the wake of Kennedy’s death. “John doesn’t toot his own horn about everything he does for the state,” he says. “I think he’s comfortable playing a behind-the-scenes role, and it’s more important for him to be a team player.”

Kerry is one of the Democratic Party’s elder statesmen. He has been in the Senate for 25 years and now is the ninth most senior Democrat in the body, out of a group of 58. Of the eight senators higher on the seniority list in Washington, Kerry, 66, is younger than all but one, Connecticut’s Christopher Dodd. If Kerry stays on in the Senate and remains healthy, he should continue to climb the seniority list, accruing benefits for Massachusetts as he goes.

Kerry says he’s ready to seize the moment. It’s one, he says, he’s long awaited: “To have a president of my party, to have a vice president who has been my friend for 25 years, to have a major committee chairmanship, and, finally, to have working majorities in the Congress.”

Kerry was just 40 when he won his seat in 1984, defeating three-term Democratic Rep. James Shannon for the nomination to replace retiring Sen. Paul Tsongas. He then defeated businessman Ray Shamie in the general election. With the exception of the 1996 race, when Kerry defeated the popular GOP Gov. William Weld, he has never faced a serious challenge.

But Kennedy, at the time of his death, was the second most senior Democrat in the Senate and was heralded in his obituaries as one of the greatest senators ever, largely because he was able to tackle state needs and shape major legislation affecting the nation. It’s a legacy that would be nearly impossible for anyone to live up to.

“To put it very simply, we will all have to work a hundred times as hard to try to make up for his loss, but even then his loss will be felt,” says McGovern of Kennedy. “We’re talking about a guy who spent decades in the Senate, mastered every maneuver, built friendships and relationships and alliances across party lines. It’s that lifetime of experience that made him irreplaceable.”

Christopher Anderson, the president of the Massachusetts High Technology Council, who teamed with Kennedy to save Massachusetts’s military bases in 2005, says Kennedy was one of a kind. “There is not going to be another Ted Kennedy and it’s unfair to expect John Kerry to be Ted Kennedy.”

But Kerry’s closest allies — including former staffers and his colleagues on Capitol Hill — say that while Kerry isn’t Kennedy, it would be unfair to pigeonhole him as someone only interested in high-profile issues like Afghanistan and global warming, or someone not willing to tackle less prestigious assignments to benefit his state. For example, Kerry retains a keen interest in the far less glamorous task of promoting small businesses. For 12 years, from 1997 to 2009, Kerry was the top Democrat on the Senate’s Small Business and Entrepreneurship Committee. There he often worked across party lines to reduce federal red tape for small companies and help them grow.

Kennedy, by contrast, was chairman of the Senate’s Health, Education, Labor and Pensions Committee, which gave him broad influence on a range of social issues important to Massachusetts residents.

Still, Kerry took the less prestigious assignment seriously, and his interest in the concerns of entrepreneurs has not fallen by the wayside since he gave up the panel chairmanship to take Vice President Joe Biden’s slot at the Foreign Relations Committee. This year, Kerry is pushing legislation that would direct federal small business loans to nonprofit child care centers and to doctors to help them modernize their patient records systems. In October, he helped secure $230 million from the Treasury Department to help Massachusetts lending institutions increase credit for underserved populations in the state. And when the Senate Finance Committee passed its health care reform bill in October, Kerry ensured that it would include a tax credit for small businesses that provide insurance to their employees. When the bill went to the Senate floor, Kerry fought to reduce the health care bill’s tax on medical device manufacturers, who represent a growing part of the Massachusetts economy.

The biggest concern about Kerry is his ability to bring home the bacon. Anderson says Kennedy’s loss will be hardest felt in that area. “It’s pretty much beyond debate how extremely effective Kennedy was at delivering federal financial resources to the region to support the technology, health care, or education communities,” he says. “It’s with that particular capacity that I think there’s a tremendous void.”

Kerry ranked 38th in the Senate in fiscal 2009 in procuring earmark funding for local projects, securing $171 million for 148 projects, according to the nonpartisan Center for Responsive Politics. Kerry-sponsored projects ranged from $160,000 in federal grants for research aimed at increasing cranberry and blueberry yields at the University of Massachusetts at Dartmouth to $1.5 million to renovate the New Bedford Whaling Museum.

In reality, though, perceptions of Kerry’s work may be less positive than the reality, which is that Kerry wasn’t too far behind Kennedy in winning earmarks. The center credited Kennedy with securing $180 million for 156 projects in the last fiscal year. Granted, Kennedy had been diagnosed with brain cancer in May 2008, requiring him to spend considerable time away from the Senate while seeking treatment. But even in fiscal 2008, Kerry wasn’t far behind Kennedy, according to the center’s data, pulling in $240 million for 133 projects. Kennedy edged him out with $260 million for 130 projects. Kerry says that he and Kennedy often teamed up on their appropriations requests. (Before fiscal 2008, senators were not required to reveal earmarked funding requests they’d sponsored.)

“John Kerry has always done his work,” says John Tierney, the seven-term representative from Salem. “You can’t belittle that. If we House members do what needs to be done, we know that we don’t have to worry about John Kerry working hard to finish the job.”

Fortuitously for Massachusetts, its House delegation, rather than launch a bitter internecine battle for Kennedy’s Senate seat, decided to shepherd its seniority. Two of those senior representatives who considered running for Kerry’s seat in 2004, if Kerry had beaten George W. Bush to become president, decided instead to stay put when Kennedy’s seat opened up. Barney Frank remains chairman of the Financial Services Committee. Edward Markey is a senior member of the House Energy and Commerce Committee. Both are among the most influential members of the House Democratic caucus. In addition, Tierney and McGovern are both considered rising stars.

And with that lineup still in place, Kerry says he’s content to remain a team player. “Massachusetts has a very strong delegation who has always worked together when it comes to supporting programs at home,” he says, “whether we’re working on getting funding for research and development, funding for teaching hospitals, or defense funding. And we will continue to work together in this effort.”