The week before the 2004 Democratic National Convention, John Kerry drafted his presidential nomination speech and then set off on a cross-country trip that brought him home to thousands of delegates waiting in Boston.

Four years later, the senator was back on the stump in the second-largest city in Massachusetts, seeking the votes of 60 people who had been lured to a restaurant with a free lunch and Greek pastries.

Times have changed, but Kerry insists he's as committed to seeking re-election to the Senate this fall as he was to campaigning for the White House four years ago.

"It's a different field, if you will, but it's no less important," the senator said Monday. "It's a privilege to represent this state, particularly. We have a great tradition here: Ted Kennedy and going back to John (Quincy) Adams."

"The fact is, John McCain still doesn't think it was a mistake to go to Iraq; Barack Obama knows that it was. That's judgment," Kerry said.

The senator voted in 2002 to authorize military force in Iraq but argued during his unsuccessful 2004 campaign against President Bush that war could have been avoided with more adept foreign policy.

The blend of local and national issues in Kerry's campaign-trail rhetoric highlights the balancing act he faces as he seeks his fifth Senate term.

His campaign speech sounds little different than in 2004. Since then, events at home and abroad have given resonance to his calls for energy independence and a redeployment of U.S. military forces away from Iraq.

"Twelve billion dollars a month _ a month _ are being spent in place where there was no al-Qaida and there were no weapons of mass destruction. And the place where there is al-Qaida and there are weapons of mass destruction _ Pakistan and Afghanistan _ they have ignored sufficiently that it's now at great risk," the senator told his Worcester audience this week.

Critics cite his presidential campaign as proof that Kerry's focus has wandered well beyond his home state, a charge given potency by the famed constituent-service operation of the senior senator from Massachusetts, Edward Kennedy.

With Kennedy ailing with a malignant brain tumor, Kerry now faces questions about whether he could uphold that tradition.

For the first time since being elected in 1984, Kerry has a challenger in the Democratic primary. He squares off Sept. 16 with a little-known Gloucester attorney, Edward O'Reilly. And unlike 2002, when Kerry was unopposed in the general election, the Republicans have nominated their own Senate candidate this year: Jeff Beatty, a former CIA operative and member of the Army's Delta Force.

At the same time, Kerry has become enmeshed in the 2008 presidential race. He endorsed Democrat Barack Obama just after the Illinois senator suffered a stinging loss to Hillary Rodham Clinton in the New Hampshire primary, a risky move.

That support, along with Kerry's choice of Obama as the 2004 convention keynote speaker, have fueled speculation Kerry might join an Obama administration as secretary of state or vice presidential running mate.

Kerry has dismissed all such speculation: "I'm interested in running for re-election."

The senator will address the 2008 convention next Wednesday during a segment focused on securing the nation's future. And he is campaigning with gusto, crisscrossing Massachusetts to hold "Kerry On Your Corner" town hall meetings.

He's also on statewide television with his first _ and possibly only _ primary commercial, a feel-good spot in which a wounded war veteran recounts how Kerry arranged for him to throw out the first pitch at Fenway Park on Patriot's Day.

The senator has refused to debate O'Reilly, citing his busy schedule. But Kerry takes on his critics in both his remarks and responses to audience questions.

At the Webster House restaurant, Kerry rebutted accusations that he lacks major legislative accomplishments, listing amendments he put forth that improved heating-oil funding, raised military pay by 3.5 percent and increased the military death benefit from $12,000 to $250,000.

"I'm smart enough to know that in this new way that Congress works, you very rarely get the slot where you can bring a bill that has your own name on it to the floor," Kerry said. "Usually you're trying to attach something to something else to get it passed."

The 64-year-old senator also touts his congressional seniority. He is now chairman of the Small Business Committee, the No. 3 Democrat on the Senate Foreign Relations Committee and the No. 5 Democrat on the Senate Finance Committee.

The pitch resonated with Carole Thompson, a Worcester psychologist in the audience.

"He tried to represent the party, and it's unfortunate the Republicans find a way to make devils out of heroes," Thompson said. "Besides, we need another Democrat in the Senate."