With the Iraq conflict the number-one national issue on US voters' minds, Mr Bush and his Republicans pounced on Senator Kerry's comment that those who neglect their education "get stuck in Iraq" and demanded he apologise to the roughly 150,000 US troops there.
Mr Bush, looking to energise party activists ahead of the November
7 elections, called the remarks "insulting" and "shameful," and Senator Kerry shot back that the charge was a "crazy" distortion of what he said.
Voter anger over Iraq, where 100 US soldiers have died in October alone and more than 2,800 have lost their lives since the US-led March 2003 invasion, has weighed heavily on the president and his party.
Senator Kerry had earlier told a college audience: "You know, education, if you make the most of it, you study hard, you do your homework and you make an effort to be smart, you can do well. If you don't, you get stuck in Iraq."
Republicans -- worried that the war could cost them control of the House of Representatives, the Senate, or both on November 7 -- seized on Senaotr Kerry's comment to emphasize their theme that the Democrats are weak on national security.
That led the senator, a decorated Vietnam War veteran, to counter that his comments were "a botched joke about the president and the president's people, not about the troops."
"If anybody thinks that a veteran would somehow criticise more than 140,000 troops serving in Iraq and not the president and his people who put them there, they're crazy," he told reporters.
"This president and his administration didn't do their homework. They didn't study what would happen in Iraq. They didn't study and listen to the people who were the experts and would have told them. And they know that's what I was talking about," said Mr Kerry.
Speaking to a raucous Republican rally in this southern state, Mr Bush said: "The senator's suggestion that the men and women of our military are somehow uneducated is insulting and it is shameful."
"The members of the United States military are plenty smart, and they are plenty brave, and the senator from Massachusetts owes them an apology," President Bush said.
Senator Kerry shot back: "If anyone owes our troops in the fields an apology, it is the president and his failed team and a Republican majority in the Congress that has been willing to rubber-stamp policies that have done injury to our troops and to their families."
Democrats, heartened by polls giving them an edge nationwide and in a handful of key races, need 15 seats to take control of the 435-seat House of Representatives and six seats to capture the 100-seat Senate.
The war of words recalled the bitter rhetoric of Mr Bush and Senator Kerry's 2004 battle for the White House -- as well as some of Mr Kerry's previous verbal missteps -- even though neither man is seeking re-election.