He still jets across the country, raising millions of dollars and rallying Democrats. He still stalks the TV news show circuit, scolding President Bush at every turn.
His campaign Web site boasts of an online army of 3 million supporters.
The Massachusetts Democrat, defeated by President Bush in 2004, insists it is far too early to talk about the 2008 race, but some analysts assume he has already positioning himself for another shot at the White House.
"Obviously, Kerry has all but said he wants another crack at the thing," said Neal Thigpen, a political science professor at South Carolina's Francis Marion University. "He's going to make a second try."
While most losing presidential nominees quickly fade into the political landscape, Kerry has worked hard at maintaining a high public profile.
"He's continuing the fight he began in 2004," said Kerry spokesman David Wade. "He wants to make it very clear he's a fighter who is going to continue to fight for his agenda."
Borrowing a page from Republican Sen. John McCain's 2000 post-election playbook, Kerry has kept much of his presidential political organization intact. He has also used his fundraising prowess to aid Democrats across the country, collecting chits that could be called if he seeks the party's White House nomination.
"He believes in his heart and soul that he came just a whisker away from being president," said Ronald Kaufman, a veteran GOP operative with Massachusetts roots.
Traveling extensively since his 2004 loss, Kerry generated nearly $5.3 million for dozens of Democratic candidates, state parties and charitable causes, according to aides.
He gave more than $200,000 to help Washington state Democrats prevail in Christine Gregoire's gubernatorial recount.
Kerry has expanded his campaign's e-mail supporter list, a vital organizing tool if he runs again. He has bought TV and newspaper ads promoting pet issues such as children's health care and his opposition to oil drilling in the Arctic National Wildlife Refuge. He also reunited several members of his campaign policy team.
"No other past presidential candidate, with the exception of McCain, has done what Kerry has done in terms of converting his presidential campaign into a grass-roots political and legislative operation," said Wade. "He's dedicated to electing Democrats."
Despite such political spadework, Kerry can expect an uphill fight in 2008.
"He is going to have a difficult time overcoming his last campaign and explaining to the party regulars how and why he lost," said Dan Payne, a longtime Democratic consultant and former Kerry strategist. "There's only so much that the Democrats can blame on (senior Bush adviser) Karl Rove."
Kerry would also be bucking history. Adlai Stevenson was a two-time Democratic nominee nearly a half-century ago. He suffered back-to-back losses in 1952 and 1956 to Republican Dwight Eisenhower.
"Democrats are less prone historically to turn to a defeated nominee again," said political scientist Thigpen.
Richard Nixon won the Republican nomination in 1960, but lost the general election. He rebounded eight years later to capture the presidency.
In 2008, Democrats will probably be eager for a fresh face, said Thigpen, citing New York Sen. Hillary Clinton's lead in early polls and her ability to raise large sums of money.
"There's not a lot of fire out there for Kerry," he said.
Kerry's image as a Northeast liberal with fuzzy views on major issues like Iraq would make him vulnerable once more, said Kaufman, who was White House political director for Bush's father, President George H.W. Bush.
"I go to bed every night praying Kerry is the nominee again," he said.