Vietnam vets in particular are torn over Kerry's combat record, while support for Bush is far from solidified.
They came by motorcycle and wheelchair, one group in a small boat symbolically crossing Boston Harbor. Some wore suits and ties, others faded fatigues with battle ribbons and personal decorations.
Hundreds of military veterans have joined John Kerry's campaign for the presidency. It's a calculated part of Senator Kerry's effort to display "a lifetime of strength and service" - one of the major themes of this week's Democratic National Convention. But it's also a gut-level response to having the first Vietnam combat vet just one election away from becoming commander in chief.
"They are there because they love and respect him," says Max Cleland, the former US Senator from Georgia who lost three limbs to a grenade in Vietnam. Mr. Cleland is scheduled to introduce Kerry in Boston.
Wednesday, 12 retired generals and admirals - an impressive amount of brass by any standard - endorsed Kerry for president.
"By not bringing in our friends and allies, [Bush administration officials] have created a mess in Iraq and are crippling our forces around the world," said retired US Navy Admiral William Crowe, former chairman of the Joint Chiefs of Staff. "John Kerry has a realistic understanding of the requirements of our military and the threats that we face."
But it's also a risky move for the challenger, especially in wartime.
Veterans generally, and Vietnam vets in particular, are torn over Kerry's combat record and antiwar experience, and also over his work with fellow Sen. John McCain (R) of Arizona to normalize relations with Vietnam and to dispel conspiracy theories about left-behind POWs.
That background also has dredged up public feelings and perceptions about the war like no presidential election since 1972. Obviously Kerry can't ignore it, so he's playing it as a strength - featuring many vets in prominent positions in the campaign and convention, especially former shipmates on the river patrol boats he commanded offering personal testimonials.
"The support of vets for John Kerry is unprecedented," says John Hurley, an Army vet of the Vietnam War who heads the veterans' part of the Kerry campaign. "There was a sense among vets back in Iowa and New Hampshire that he's for us." Cleland says the 100,000 vets signed up to work for Kerry is a number "growing every day."